scholarly journals Modelling the incubation microclimate to predict offspring sex ratios and hatching phenology in tuatara (Sphenodon punctatus)

2021 ◽  
Author(s):  
◽  
Anna L. Carter
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Embryonic Development ◽  
Climate Warming ◽  
Sex Ratios ◽  
Warming Scenario ◽  
Offspring Sex ◽  
Nesting Behaviour ◽  
Sphenodon Punctatus ◽  
Hatching Phenology

<p>Successful conservation of terrestrial biodiversity requires understanding and predicting the impacts of rapid climate warming on the suitability of both current and potential future habitats. Most predictions of range shifts and other population-scale effects of climate change rely to some extent on statistical links between a species' known geographical distribution and the suite of environmental conditions experienced within that space. However, species' responses to climate change are likely to be more complex than can be represented by the projection of current species-environment relationships into unknown environments. An important goal in biodiversity conservation is the development of quantitative tools with which to assess habitat suitability independently of distributions.  In populations of oviparous species, climate change and habitat modification may have distinct effects on different life stages. Temperatures that are well within the thermal tolerance range of adults, for example, may affect embryonic development rates, hatching phenology, or offspring survival and phenotype. I examined how environmental variation may affect the thermal suitability of habitat for facilitating embryonic development and maintaining balanced sex ratios in tuatara (Sphenodon punctatus), an endemic New Zealand reptile with temperature-dependent sex determination (TSD). Once widespread throughout New Zealand, populations are now restricted to offshore islands and fenced mainland sanctuaries, though establishment of additional populations via translocation is ongoing. Due to intensive conservation efforts, tuatara are not classified as an endangered species, but, like other species in which hatchling sex is determined by the incubation environment, populations are potentially at risk from the detrimental effects of sex-ratio bias.  I conducted two seasons of field work on the island of Takapourewa to quantify the relationship between rapid vegetation succession and selection of nesting areas. I then used a variety of predictive models to link data on nesting behaviour collected in the field with the microclimate conditions experienced by nesting female tuatara and developing embryos. Using mechanistically modelled soil temperature data, I generated predictions of incubation temperatures, offspring sex ratios, and hatching dates for two populations of tuatara on environmentally distinct islands, Takapourewa and Hauturu, under current and projected future climate scenarios. Finally, I classified the thermal suitability of sites on Hauturu for facilitating successful embryonic development and created geospatial surfaces defining suitable nesting locations adjacent to tuatara habitats.  Offspring sex ratios on both islands are unlikely to become male-biased if the magnitude of climate warming observed over the next century more closely matches the minimum, rather than the maximum, projected warming scenario. On Takapourewa, the timing of nesting will be critical in determining whether sex ratios become male-biased under a scenario of maximum climate warming. Earlier nesting may also lead to shifts in hatching phenology under either scenario of climate warming. Warmer annual temperatures on Hauturu are more likely to lead to heavily male-biased offspring sex ratios under the maximum warming scenario. Female tuatara on Hauturu do not need to travel away from their current habitats to locate suitable nesting sites. Monitoring the population to quantify nesting behaviour on the island will be important for determining whether females' choices of incubation microclimates can compensate for the sex ratio-biasing effects of climate change.</p>

scholarly journals Modelling the incubation microclimate to predict offspring sex ratios and hatching phenology in tuatara (Sphenodon punctatus)

2021 ◽  
Author(s):  
◽  
Anna L. Carter
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Embryonic Development ◽  
Climate Warming ◽  
Sex Ratios ◽  
Warming Scenario ◽  
Offspring Sex ◽  
Nesting Behaviour ◽  
Sphenodon Punctatus ◽  
Hatching Phenology

<p>Successful conservation of terrestrial biodiversity requires understanding and predicting the impacts of rapid climate warming on the suitability of both current and potential future habitats. Most predictions of range shifts and other population-scale effects of climate change rely to some extent on statistical links between a species' known geographical distribution and the suite of environmental conditions experienced within that space. However, species' responses to climate change are likely to be more complex than can be represented by the projection of current species-environment relationships into unknown environments. An important goal in biodiversity conservation is the development of quantitative tools with which to assess habitat suitability independently of distributions.  In populations of oviparous species, climate change and habitat modification may have distinct effects on different life stages. Temperatures that are well within the thermal tolerance range of adults, for example, may affect embryonic development rates, hatching phenology, or offspring survival and phenotype. I examined how environmental variation may affect the thermal suitability of habitat for facilitating embryonic development and maintaining balanced sex ratios in tuatara (Sphenodon punctatus), an endemic New Zealand reptile with temperature-dependent sex determination (TSD). Once widespread throughout New Zealand, populations are now restricted to offshore islands and fenced mainland sanctuaries, though establishment of additional populations via translocation is ongoing. Due to intensive conservation efforts, tuatara are not classified as an endangered species, but, like other species in which hatchling sex is determined by the incubation environment, populations are potentially at risk from the detrimental effects of sex-ratio bias.  I conducted two seasons of field work on the island of Takapourewa to quantify the relationship between rapid vegetation succession and selection of nesting areas. I then used a variety of predictive models to link data on nesting behaviour collected in the field with the microclimate conditions experienced by nesting female tuatara and developing embryos. Using mechanistically modelled soil temperature data, I generated predictions of incubation temperatures, offspring sex ratios, and hatching dates for two populations of tuatara on environmentally distinct islands, Takapourewa and Hauturu, under current and projected future climate scenarios. Finally, I classified the thermal suitability of sites on Hauturu for facilitating successful embryonic development and created geospatial surfaces defining suitable nesting locations adjacent to tuatara habitats.  Offspring sex ratios on both islands are unlikely to become male-biased if the magnitude of climate warming observed over the next century more closely matches the minimum, rather than the maximum, projected warming scenario. On Takapourewa, the timing of nesting will be critical in determining whether sex ratios become male-biased under a scenario of maximum climate warming. Earlier nesting may also lead to shifts in hatching phenology under either scenario of climate warming. Warmer annual temperatures on Hauturu are more likely to lead to heavily male-biased offspring sex ratios under the maximum warming scenario. Female tuatara on Hauturu do not need to travel away from their current habitats to locate suitable nesting sites. Monitoring the population to quantify nesting behaviour on the island will be important for determining whether females' choices of incubation microclimates can compensate for the sex ratio-biasing effects of climate change.</p>

scholarly journals Interactive effects of climate change and plant invasion on alpine biodiversity and ecosystem dynamics

2021 ◽  
Author(s):  
◽  
Justyna Giejsztowt
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Plant Species ◽  
Climate Warming ◽  
Plant Invasion ◽  
Invasive Plant ◽  
Ecosystem Dynamics ◽  
Interactive Effects ◽  
Native Plant ◽  
Competition For Pollination

<p>Drivers of global change have direct impacts on the structure of communities and functioning of ecosystems, and interactions between drivers may buffer or exacerbate these direct effects. Interactions among drivers can lead to complex non-linear outcomes for ecosystems, communities and species, but are infrequently quantified. Through a combination of experimental, observational and modelling approaches, I address critical gaps in our understanding of the interactive effects of climate change and plant invasion, using Tongariro National Park (TNP; New Zealand) as a model. TNP is an alpine ecosystem of cultural significance which hosts a unique flora with high rates of endemism. TNP is invaded by the perennial shrub Calluna vulgaris (L.) Hull. My objectives were to: 1) determine whether species-specific phenological shifts have the potential to alter the reproductive capacity of native plants in landscapes affected by invasion; 2) determine whether the effect of invasion intensity on the Species Area Relationship (SAR) of native alpine plant species is influenced by environmental stress; 3) develop a novel modelling framework that would account for density-dependent competitive interactions between native species and C. vulgaris and implement it to determine the combined risk of climate change and plant invasion on the distribution of native plant species; and 4) explore the possible mechanisms leading to a discrepancy in C. vulgaris invasion success on the North and South Islands of New Zealand. I show that species-specific phenological responses to climate warming increase the flowering overlap between a native and an invasive plant. I then show that competition for pollination with the invader decreases the sexual reproduction of the native in some landscapes. I therefore illustrate a previously undescribed interaction between climate warming and plant invasion where the effects of competition for pollination with an invader on the sexual reproduction of the native may be exacerbated by climate warming. Furthermore, I describe a previously unknown pattern of changing invasive plant impact on SAR along an environmental stress gradient. Namely, I demonstrate that interactions between an invasive plant and local native plant species richness become increasingly facilitative along elevational gradients and that the strength of plant interactions is dependent on invader biomass. I then show that the consequences of changing plant interactions at a local scale for the slope of SAR is dependent on the pervasion of the invader. Next, I demonstrate that the inclusion of invasive species density data in distribution models for a native plant leads to greater reductions in predicted native plant distribution and density under future climate change scenarios relative to models based on climate suitability alone. Finally, I find no evidence for large-scale climatic, edaphic, and vegetative limitations to invasion by C. vulgaris on either the North and South Islands of New Zealand. Instead, my results suggest that discrepancies in invasive spread between islands may be driven by human activity: C. vulgaris is associated with the same levels of human disturbance on both islands despite differences in the presence of these conditions between then islands. Altogether, these results show that interactive effects between drivers on biodiversity and ecosystem dynamics are frequently not additive or linear. Therefore, accurate predictions of global change impacts on community structure and ecosystems function require experiments and models which include of interactions among drivers such as climate change and species invasion. These results are pertinent to effective conservation management as most landscapes are concurrently affected by multiple drivers of global environmental change.</p>

scholarly journals Climates of Change: A Tuatara’s-Eye View

Humanities ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 38 ◽  
Author(s):  
Anna Boswell
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Ultraviolet Light ◽  
Vulnerable Species ◽  
Aotearoa New Zealand ◽  
The Future ◽  
Sphenodon Punctatus ◽  
Soil Temperatures ◽  
Slow Breathing

The tuatara or New Zealand “spiny-backed lizard” (Sphenodon punctatus) is the sole surviving member of an order of reptiles that pre-dates the dinosaurs. Among its characteristics and peculiarities, the tuatara is renowned for being slow-breathing and long-lived; it possesses a third eye on the top of its skull for sensing ultraviolet light; and the sex of its progeny is determined by soil temperatures. This article unravels a tuatara’s-eye view of climate change, considering this creature’s survival across geological epochs, its indigenous lineage and its sensitivities to the fast-shifting conditions of the Anthropocene. This article examines the tuatara’s evolving role as an icon of biodiversity-under-threat and the evolving role of zoos and sanctuaries as explicators of climate change, forestallers of extinction, and implementers of the reproductive interventions that are increasingly required to secure the future of climate-vulnerable species. It is also interested in the tuatara as a witness to the rapid and ongoing human-wrought climate change which has secured the lifeworld reconstruction that is foundational to the settler colonial enterprise in Aotearoa/New Zealand. Linking this to the Waitangi Tribunal’s Wai 262 report (Ko Aotearoa Tēnei, 2011), the article considers what the tuatara teaches about kaitiakitanga (guardianship) and climates of change.

scholarly journals Using conservation translocations to assess the impact of anthropogenic climate change on a cold-adapted reptile, the tuatara (Sphenodon punctatus)

2021 ◽  
Author(s):  
◽  
Stephanie J. Price
Keyword(s):  
Climate Change ◽  
Climate Warming ◽  
Anthropogenic Climate Change ◽  
Learning Ability ◽  
Conservation Strategy ◽  
Lower Latitude ◽  
Cold Adapted ◽  
Air Temperatures ◽  
Sphenodon Punctatus ◽  
The Impact

<p>Anthropogenic climate change is progressing at a rate unprecedented in the past 65 million years and is a significant conservation concern. The associated biotic and abiotic impacts are expected to have substantial effects on global biodiversity, with some species potentially more vulnerable than others. The tuatara (Sphenodon punctatus) is a New Zealand endemic reptile and of particular interest as it is a slowly reproducing, range-restricted, cold-adapted ectotherm with temperature-dependent sex determination. Consequently, tuatara could be particularly vulnerable to rising air temperatures and conservation translocations have been key components of tuatara conservation efforts. Knowledge of how the tuatara might be affected by warmer climates will help inform where future conservation efforts are best directed, practices to avoid and which sites might be most suitable for the establishment of populations. The translocation of 176 adult tuatara in October 2012 from Stephens Island in New Zealand’s Cook Strait to four latitudinally distant North Island sites offered the opportunity to study the responses of tuatara in a range of environments. The comparatively warmer, drier climates of several sites provided surrogates for temporal climate change, enabling an assessment of how a warming climate might impact tuatara, and how they might respond. Using field observations, laboratory analysis and controlled experiments I investigated the short-term success of the translocations, the influence of translocation and climate on tuatara enteric bacterial communities and parasites, as well as how warmer climates might influence nocturnal activity, thermoregulatory opportunities and learning ability. I found several translocated populations to be progressing favourably, and found evidence that tuatara may exhibit enhanced growth at warmer, less densely-populated sites, suggesting that further translocations to lower latitude sites might be a viable conservation strategy. However, high population density at one translocation site was a concern and management recommendations were made to enable the dispersal of individuals. I detected Salmonella Saintpaul for the first time in a live tuatara, Campylobacter spp. was identified as a likely common commensal organism, and no measurable impact of translocation or climate on bacterial prevalence was observed, suggesting no substantial risk of climate warming to the susceptibility of tuatara to these bacteria. Tick populations were negatively impacted by translocation-associated factors following release but subsequently recovered at most sites and mites were not found on any translocated tuatara. Diurnal and nocturnal activities were positively influenced by air temperature, up to an upper threshold, and assessment of the site-specific thermal climates suggested that tuatara at warmer sites may benefit from increased opportunities for emergence and the attainment of preferred body temperatures throughout the year, though a higher frequency of restrictive air temperatures over summer may also reduce emergence opportunities. Experimental work showed that warmer air temperatures may enhance learning in tuatara, which could improve their ability to cope with challenging environments under climate change. However, body size was also an influential component of learning ability and further research is needed to build on these initial findings. I conclude that tuatara may experience overall benefits from further translocations to warmer sites and warming climates at currently cooler sites, which suggests that other cold-adapted reptiles with similar thermal tolerances may also see initial benefits under climate warming, though further monitoring is required to determine longer-term translocation success. Equally, while warmer air temperatures were not found to be detrimental to tuatara, they still pose a risk to population viability and further work is required on the impacts of associated abiotic factors like drought, and how populations of this long-lived species may be affected if and when climate warming exceeds the upper temperature rise of ~5°C predicted by the 2100s.</p>

scholarly journals Using conservation translocations to assess the impact of anthropogenic climate change on a cold-adapted reptile, the tuatara (Sphenodon punctatus)

2021 ◽  
Author(s):  
◽  
Stephanie J. Price
Keyword(s):  
Climate Change ◽  
Climate Warming ◽  
Anthropogenic Climate Change ◽  
Learning Ability ◽  
Conservation Strategy ◽  
Lower Latitude ◽  
Cold Adapted ◽  
Air Temperatures ◽  
Sphenodon Punctatus ◽  
The Impact

<p>Anthropogenic climate change is progressing at a rate unprecedented in the past 65 million years and is a significant conservation concern. The associated biotic and abiotic impacts are expected to have substantial effects on global biodiversity, with some species potentially more vulnerable than others. The tuatara (Sphenodon punctatus) is a New Zealand endemic reptile and of particular interest as it is a slowly reproducing, range-restricted, cold-adapted ectotherm with temperature-dependent sex determination. Consequently, tuatara could be particularly vulnerable to rising air temperatures and conservation translocations have been key components of tuatara conservation efforts. Knowledge of how the tuatara might be affected by warmer climates will help inform where future conservation efforts are best directed, practices to avoid and which sites might be most suitable for the establishment of populations. The translocation of 176 adult tuatara in October 2012 from Stephens Island in New Zealand’s Cook Strait to four latitudinally distant North Island sites offered the opportunity to study the responses of tuatara in a range of environments. The comparatively warmer, drier climates of several sites provided surrogates for temporal climate change, enabling an assessment of how a warming climate might impact tuatara, and how they might respond. Using field observations, laboratory analysis and controlled experiments I investigated the short-term success of the translocations, the influence of translocation and climate on tuatara enteric bacterial communities and parasites, as well as how warmer climates might influence nocturnal activity, thermoregulatory opportunities and learning ability. I found several translocated populations to be progressing favourably, and found evidence that tuatara may exhibit enhanced growth at warmer, less densely-populated sites, suggesting that further translocations to lower latitude sites might be a viable conservation strategy. However, high population density at one translocation site was a concern and management recommendations were made to enable the dispersal of individuals. I detected Salmonella Saintpaul for the first time in a live tuatara, Campylobacter spp. was identified as a likely common commensal organism, and no measurable impact of translocation or climate on bacterial prevalence was observed, suggesting no substantial risk of climate warming to the susceptibility of tuatara to these bacteria. Tick populations were negatively impacted by translocation-associated factors following release but subsequently recovered at most sites and mites were not found on any translocated tuatara. Diurnal and nocturnal activities were positively influenced by air temperature, up to an upper threshold, and assessment of the site-specific thermal climates suggested that tuatara at warmer sites may benefit from increased opportunities for emergence and the attainment of preferred body temperatures throughout the year, though a higher frequency of restrictive air temperatures over summer may also reduce emergence opportunities. Experimental work showed that warmer air temperatures may enhance learning in tuatara, which could improve their ability to cope with challenging environments under climate change. However, body size was also an influential component of learning ability and further research is needed to build on these initial findings. I conclude that tuatara may experience overall benefits from further translocations to warmer sites and warming climates at currently cooler sites, which suggests that other cold-adapted reptiles with similar thermal tolerances may also see initial benefits under climate warming, though further monitoring is required to determine longer-term translocation success. Equally, while warmer air temperatures were not found to be detrimental to tuatara, they still pose a risk to population viability and further work is required on the impacts of associated abiotic factors like drought, and how populations of this long-lived species may be affected if and when climate warming exceeds the upper temperature rise of ~5°C predicted by the 2100s.</p>

scholarly journals Evolutionary and demographic consequences of temperature-induced masculinization under climate warming: the effects of mate choice

2020 ◽  
Author(s):  
Edina Nemesházi ◽  
Szilvia Kövér ◽  
Veronika Bókony
Keyword(s):  
Climate Change ◽  
Mate Choice ◽  
Sex Determination ◽  
Climate Warming ◽  
Sex Chromosome ◽  
Global Climate ◽  
Sex Ratios ◽  
Phenotypic Traits ◽  
System Transformation ◽  
Sex Determination System

AbstractBackgroundOne of the dangers of global climate change to wildlife is distorting sex ratios by temperature-induced sex reversals in populations where sex determination is not exclusively genetic, potentially leading to population collapse and/or sex-determination system transformation. Here we introduce a new concept on how these outcomes may be altered by mate choice if sex-chromosome-linked phenotypic traits allow females to choose between normal and sex-reversed (genetically female) males.ResultsWe developed a theoretical model to investigate if preference for sex-reversed males would spread and affect demographic and evolutionary processes under climate warming. We found that preference for sex-reversed males 1) more likely spread in ZW/ZZ than in XX/XY sex-determination systems, 2) in populations starting with ZW/ZZ system, it significantly hastened the transitions between different sex-determination systems and maintained more balanced adult sex ratio for longer compared to populations where all females preferred normal males; and 3) in ZZ/ZW systems with low but nonzero viability of WW individuals, a widespread preference for sex-reversed males saved the populations from early extinction.ConclusionsOur results suggest that climate change may affect the evolution of mate choice, which in turn may influence the evolution of sex-determination systems, sex ratios, and thereby adaptive potential and population persistence.

scholarly journals Spatial and temporal variation in nest temperatures forecasts sex ratio skews in a crocodilian with environmental sex determination

2020 ◽  
Vol 287 (1926) ◽  
pp. 20200210
Author(s):  
Samantha L. Bock ◽  
Russell H. Lowers ◽  
Thomas R. Rainwater ◽  
Eric Stolen ◽  
John M. Drake ◽  
...  
Keyword(s):  
Climate Change ◽  
Sex Ratio ◽  
Sex Determination ◽  
Temperature Variation ◽  
Climatic Factors ◽  
Sex Ratios ◽  
Alligator Mississippiensis ◽  
Spatial And Temporal Variation ◽  
Nest Temperature ◽  
Offspring Sex

Species displaying temperature-dependent sex determination (TSD) are especially vulnerable to the effects of a rapidly changing global climate due to their profound sensitivity to thermal cues during development. Predicting the consequences of climate change for these species, including skewed offspring sex ratios, depends on understanding how climatic factors interface with features of maternal nesting behaviour to shape the developmental environment. Here, we measure thermal profiles in 86 nests at two geographically distinct sites in the northern and southern regions of the American alligator's ( Alligator mississippiensis ) geographical range, and examine the influence of both climatic factors and maternally driven nest characteristics on nest temperature variation. Changes in daily maximum air temperatures drive annual trends in nest temperatures, while variation in individual nest temperatures is also related to local habitat factors and microclimate characteristics. Without any compensatory nesting behaviours, nest temperatures are projected to increase by 1.6–3.7°C by the year 2100, and these changes are predicted to have dramatic consequences for offspring sex ratios. Exact sex ratio outcomes vary widely depending on site and emission scenario as a function of the unique temperature-by-sex reaction norm exhibited by all crocodilians. By revealing the ecological drivers of nest temperature variation in the American alligator, this study provides important insights into the potential consequences of climate change for crocodilian species, many of which are already threatened by extinction.

scholarly journals Evolutionary and demographic consequences of temperature-induced masculinization under climate warming: the effects of mate choice

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Edina Nemesházi ◽  
Szilvia Kövér ◽  
Veronika Bókony
Keyword(s):  
Climate Change ◽  
Mate Choice ◽  
Sex Determination ◽  
Climate Warming ◽  
Sex Chromosome ◽  
Global Climate ◽  
Sex Ratios ◽  
Sex Reversal ◽  
Phenotypic Traits ◽  
System Transformation

Abstract Background One of the dangers of global climate change to wildlife is distorting sex ratios by temperature-induced sex reversals in populations where sex determination is not exclusively genetic, potentially leading to population collapse and/or sex-determination system transformation. Here we introduce a new concept on how these outcomes may be altered by mate choice if sex-chromosome-linked phenotypic traits allow females to choose between normal and sex-reversed (genetically female) males. Results We developed a theoretical model to investigate if an already existing autosomal allele encoding preference for sex-reversed males would spread and affect demographic and evolutionary processes under climate warming. We found that preference for sex-reversed males (1) more likely spread in ZW/ZZ than in XX/XY sex-determination systems, (2) in populations starting with ZW/ZZ system, it significantly hastened the transitions between different sex-determination systems and maintained more balanced adult sex ratio for longer compared to populations where all females preferred normal males; and (3) in ZW/ZZ systems with low but non-zero viability of WW individuals, a widespread preference for sex-reversed males saved the populations from early extinction. Conclusions Our results suggest that climate change may affect the evolution of mate choice, which in turn may influence the evolution of sex-determination systems, sex ratios, and thereby adaptive potential and population persistence. These findings show that preferences for sex-linked traits have special implications in species with sex reversal, highlighting the need for empirical research on the role of sex reversal in mate choice.

scholarly journals Interactive effects of climate change and plant invasion on alpine biodiversity and ecosystem dynamics

2021 ◽  
Author(s):  
◽  
Justyna Giejsztowt
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Plant Species ◽  
Climate Warming ◽  
Plant Invasion ◽  
Invasive Plant ◽  
Ecosystem Dynamics ◽  
Interactive Effects ◽  
Native Plant ◽  
Competition For Pollination

<p>Drivers of global change have direct impacts on the structure of communities and functioning of ecosystems, and interactions between drivers may buffer or exacerbate these direct effects. Interactions among drivers can lead to complex non-linear outcomes for ecosystems, communities and species, but are infrequently quantified. Through a combination of experimental, observational and modelling approaches, I address critical gaps in our understanding of the interactive effects of climate change and plant invasion, using Tongariro National Park (TNP; New Zealand) as a model. TNP is an alpine ecosystem of cultural significance which hosts a unique flora with high rates of endemism. TNP is invaded by the perennial shrub Calluna vulgaris (L.) Hull. My objectives were to: 1) determine whether species-specific phenological shifts have the potential to alter the reproductive capacity of native plants in landscapes affected by invasion; 2) determine whether the effect of invasion intensity on the Species Area Relationship (SAR) of native alpine plant species is influenced by environmental stress; 3) develop a novel modelling framework that would account for density-dependent competitive interactions between native species and C. vulgaris and implement it to determine the combined risk of climate change and plant invasion on the distribution of native plant species; and 4) explore the possible mechanisms leading to a discrepancy in C. vulgaris invasion success on the North and South Islands of New Zealand. I show that species-specific phenological responses to climate warming increase the flowering overlap between a native and an invasive plant. I then show that competition for pollination with the invader decreases the sexual reproduction of the native in some landscapes. I therefore illustrate a previously undescribed interaction between climate warming and plant invasion where the effects of competition for pollination with an invader on the sexual reproduction of the native may be exacerbated by climate warming. Furthermore, I describe a previously unknown pattern of changing invasive plant impact on SAR along an environmental stress gradient. Namely, I demonstrate that interactions between an invasive plant and local native plant species richness become increasingly facilitative along elevational gradients and that the strength of plant interactions is dependent on invader biomass. I then show that the consequences of changing plant interactions at a local scale for the slope of SAR is dependent on the pervasion of the invader. Next, I demonstrate that the inclusion of invasive species density data in distribution models for a native plant leads to greater reductions in predicted native plant distribution and density under future climate change scenarios relative to models based on climate suitability alone. Finally, I find no evidence for large-scale climatic, edaphic, and vegetative limitations to invasion by C. vulgaris on either the North and South Islands of New Zealand. Instead, my results suggest that discrepancies in invasive spread between islands may be driven by human activity: C. vulgaris is associated with the same levels of human disturbance on both islands despite differences in the presence of these conditions between then islands. Altogether, these results show that interactive effects between drivers on biodiversity and ecosystem dynamics are frequently not additive or linear. Therefore, accurate predictions of global change impacts on community structure and ecosystems function require experiments and models which include of interactions among drivers such as climate change and species invasion. These results are pertinent to effective conservation management as most landscapes are concurrently affected by multiple drivers of global environmental change.</p>

scholarly journals Effects of climate warming on the distribution of C4 grasses in New Zealand

1990 ◽  
pp. 47-50 ◽  
Author(s):  
T.R.O. Field ◽  
M.B. Forde
Keyword(s):  
Climate Change ◽  
New Zealand ◽  
Climate Warming ◽  
Frost Tolerance ◽  
C4 Grasses ◽  
The Public ◽  
C4 Species ◽  
Recent Climate ◽  
Annual Summer ◽  
Improved Pasture

Data from pasture and roadside surveys and from an appeal to the public were used to assess whether recent climate warming has increased the spread of C4 grasses. Because of differences in date of introduction, saturation of existing range, ability to spread by seed, frost tolerance, and soil and moisture requirements, each species studied had a different potential increase in response to higher temperatures. Also spread could be exhibited as greater abundance within existing range as well as increase in geographical range. The strongest evidence that could be construed as an effect of climate warming was an increase of about 1.5" latitude in the area of 40% pasture occurrence of paspalum in the last 10-12 years. In the same period both carpet grass and knot-root bristle grass also greatly increased their impact. Most of the species studied (including the annual summer grass) underwent an explosive increase in the last 2-3 years after several particularly mild winters and warm summers. C4 species will probably be an increasing feature of pastures and lawns in future, and this should be accommodated by appropriate management and the introduction of improved pasture and amenity cultivars of this type. Keywords C4 grasses, climate change, paspalum, pasture survey

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