Environmental suitability models predict population density, performance and body condition for microendemic salamanders

Conspecific density is widely recognized as an important ecological factor across the animal kingdom; however, the physiological impacts are less thoroughly described. In fact, population density is rarely mentioned as a factor in physiological studies on captive animals and, when it is infrequently addressed, the animals used are reared and housed at densities far above those in nature, making the translation of results from the laboratory to natural systems difficult. We survey the literature to highlight this important ecophysiological gap and bring attention to the possibility that conspecific density prior to experimentation may be a critical factor influencing results. Across three taxa: mammals, birds, and fish, we present evidence from ecology that density influences glucocorticoid levels, immune function, and body condition with the intention of stimulating discussion and increasing consideration of population density in physiology studies. We conclude with several directives to improve the applicability of insights gained in the laboratory to organisms in the natural environment.

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Which processes are behind the relationship between species abundance and environmental suitability? Monte Albo cave salamander as model species

ARPHA Conference Abstracts ◽

10.3897/aca.1.e29834 ◽

2018 ◽

Vol 1 ◽

Author(s):

Enrico Lunghi ◽

Raoul Manenti ◽

Manuela Mulargia ◽

Michael Veith ◽

Claudia Corti ◽

...

Keyword(s):

Body Condition ◽

Species Abundance ◽

Strong Relationship ◽

Individual Performance ◽

Activity Level ◽

Activity Levels ◽

Limited Information ◽

Model Species ◽

Distribution Models ◽

Environmental Suitability

Species can show a strong variation of local abundance across their ranges. Recent analyses suggested that variation in abundance can be related to environmental suitability, as the highest abundances are often observed in populations living in the most suitable areas. However, there is limited information on the mechanisms through which variation in environmental suitability determines abundance. We analyzed populations of the microendemic Monte Albo cave salamander Hydromantes (Speleomantes) flavus Stefani, 1969 (Plethodontidae), and tested several hypotheses on potential relationships linking environmental suitability to population parameters. For multiple populations across the whole species range, we assessed suitability using species distribution models and measured density, activity level, food intake, and body condition index. In high-suitability sites, the density of salamanders was up to 30 times higher than in the least suitable ones. Variation in activity levels and population performance can explain such variation of abundance. In high-suitability sites, salamanders were active close to the surface and showed a low frequency of empty stomachs. Furthermore, when taking into account seasonal variation, body condition was better in the most suitable sites. Our results show that the strong relationship between environmental suitability and population abundance can be mediated by the variation of parameters strongly linked to individual performance and fitness. Furthermore, we highlighted the potential use of cave animals as model species to answer macroecological questions.

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Global patterns of aegyptism without arbovirus

10.1101/2020.07.20.212209 ◽

2020 ◽

Author(s):

Mark F. Olson ◽

José G. Juarez ◽

Moritz U. G. Kraemer ◽

Jane P. Messina ◽

Gabriel L. Hamer

Keyword(s):

Population Density ◽

Virus Transmission ◽

Mosquito Vector ◽

Environmental Suitability ◽

Dengue Transmission ◽

The World ◽

Increasing Risk ◽

Global Patterns ◽

Lower Population ◽

Autochthonous Transmission

ABSTRACTThe world’s most important mosquito vector of viruses, Aedes aegypti, is found around the world in tropical, subtropical and even some temperate locations. While climate change may limit populations of Ae. aegypti in some regions, increasing temperatures will likely expand its territory thus increasing risk of human exposure to arboviruses in places like Europe, Northern Australia and North America, among many others. Most studies of Ae. aegypti biology and virus transmission focus on locations with high endemicity or severe outbreaks of human amplified urban arboviruses, such as dengue, Zika, and chikungunya viruses, but rarely on areas at the margins of endemicity. Our objective in this study is to explore global patterns in the environmental suitability for Ae. aegypti and dengue virus to reveal deviations in the probability of the vector and human disease occurring. We developed a map showing one end of the gradient being higher suitability of Ae. aegypti with low suitability of dengue and the other end of the spectrum being equal and higher environmental suitability for both Ae. aegypti and dengue. The regions of the world with Ae. aegypti environmental suitability and no endemic dengue transmission exhibits a phenomenon we term ‘aegyptism without arbovirus’. We then tested what environmental and socioeconomic variables influence this deviation map revealing a significant association with population density, suggesting that locations with lower population density were more likely to have a higher probability of aegyptism without arbovirus. Characterizing regions of the world with established populations of Ae. aegypti but little to no autochthonous transmission of human-amplified arboviruses is an important step in understanding and achieving aegyptism without arbovirus.

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Agricultural land use alters trophic status and population density of deer mice (Peromyscus maniculatus) on the North American Great Plains

Canadian Journal of Zoology ◽

10.1139/z2012-055 ◽

2012 ◽

Vol 90 (7) ◽

pp. 868-874 ◽

Cited By ~ 8

Author(s):

A.J. White ◽

R.G. Poulin ◽

B. Wissel ◽

J.L. Doucette ◽

C.M. Somers

Keyword(s):

Land Use ◽

Population Density ◽

Body Condition ◽

Trophic Level ◽

Trophic Status ◽

Agricultural Land ◽

Peromyscus Maniculatus ◽

Deer Mice ◽

Agricultural Land Use ◽

Native Prairie

Habitat conversion is among the most important causes of environmental change worldwide, yet relatively little is known about its potential influence on trophic interactions. We investigated the effects of agricultural land use on carbon and nitrogen stable isotope values, trophic status, population density, and body condition of deer mice ( Peromyscus maniculatus (Wagner, 1845)) in a grassland ecosystem. Muscle δ15N (cropland = 7.6‰ ± 1.3‰; hay fields = 7.9‰ ± 1.3‰; native prairie = 7.2‰ ± 2.1‰) from deer mice did not vary with land use despite baseline soil and vegetation δ15N differences. Enrichment of deer mice over vegetation (Δδ15N) was, on average, a full trophic level (~2.5‰) higher on native prairie (6.4‰ ± 1.6‰) than on cropland (3.9‰ ± 2.3‰), and intermediate in hay fields (5.9‰ ± 2.0‰). Relative density of deer mice was more than twofold higher in crop and hay fields compared with native prairie, but body condition did not vary with land use. Our results suggest that agricultural activity caused a shift in the trophic level and relative abundance of a generalist grassland omnivore. Soil and vegetation δ15N reflected anthropogenic N inputs to agricultural fields but were not useful as general markers of habitat use in this study.

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Population growth, movements, and status of the Nushagak Peninsula Caribou Herd following reintroduction, 1988 - 2000

Rangifer ◽

10.7557/2.23.5.1695 ◽

2003 ◽

Vol 23 (5) ◽

pp. 143 ◽

Cited By ~ 2

Author(s):

Gail H. Collins ◽

Michael T. Hinkes ◽

Andrew R. Aderman ◽

James D. Woolington

Keyword(s):

Population Dynamics ◽

Population Density ◽

Home Range ◽

Body Condition ◽

Canis Lupus ◽

Rangifer Tarandus ◽

Ursus Arctos ◽

Range Condition ◽

Calf Survival ◽

Population Mortality

Barren ground caribou (Rangifer tarandus) were reintroduced to the Nushagak Peninsula, Alaska in February of 1988 after an absence of more than 100 years. Since reintroduction, herd growth and population dynamics have been monitored closely. At this time, there has been no significant dispersal from the herds' core range. The Nushagak Peninsula Caribou Herd (NPCH) grew rapidly from 146 reintroduced individuals to over 1000 in 13 years. Dramatic mean annual growth during the first 6 years (1988-1994) of 38% (r = 0.32) can be attributed to the high percentage of females in the initial reintroduction, high calf production and survival, exceptional range conditions, few predators, and no hunting. However, the populations' exceptional growth (peak counts of 1400) slowed and stabilized between 1996¬1998 and then decreased between 1998 and 2000. Size, body condition and weights of calves captured in 2000 were significantly lower than those captured in 1995 and 1997. Although calf production also decreased from close to 100% (1990-1995) to about 91% (1996-2000), overall calf survival continued to be high. Legal harvest began in 1995, and harvest reports have accounted for approximately 3% of population mortality annually. Although brown bears (Ursus arctos) and wolves (Canis lupus) are present, the extent of predation is unknown. Mean home range of the NPCH was 674 km2 and group sizes were greatest during post-calving aggregation in July (mean = 127). Caribou population density on the Nushagak Peninsula reached approximately 1.2 caribou/km2 in 1997 before declining to about 1.0 caribou/km2. A range survey in 1994 noted only trace utilization of lichens on the Nushagak Peninsula by caribou. A subsequent survey in 1999 found moderate to severe utilization in 46% of plots, suggesting the reintroduced herd was beginning to alter range condition. Between 1997 and 2000, both calf production and condition of 10-month-old calves declined. Calving has also been delayed in recent years. However, we suspect the reduced herd growth can be attributed to increasing hunting pressure and some dispersal of caribou from the Peninsula, not reduced range condition.

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opinion: Relationship between local population density and environmental suitability estimated from occurrence data

Frontiers of Biogeography ◽

10.21425/f53212408 ◽

2012 ◽

Vol 3 (2) ◽

Author(s):

Alberto Jiménez‐Valverde

Keyword(s):

Population Density ◽

Local Population ◽

Environmental Suitability ◽

Occurrence Data

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Factors influencing annual variation in breeding by common brushtail possums (Trichosurus vulpecula) in New Zealand

Wildlife Research ◽

10.1071/wr00074 ◽

2002 ◽

Vol 29 (1) ◽

pp. 39 ◽

Cited By ~ 18

Author(s):

Dave Ramsey ◽

Murray Efford ◽

Phil Cowan ◽

Jim Coleman

Keyword(s):

New Zealand ◽

Population Density ◽

Body Condition ◽

Annual Variation ◽

Environmental Predictors ◽

Major Exception ◽

Individual Condition ◽

Average Body ◽

Long Term Studies

We assembled data on annual variation in breeding rates of brushtail possums from four long-term studies in the lower North Island of New Zealand, three of which spanned more than 20 years. In each study, more than 80% of adult females bred in most years. The major exception was in 1996, when breeding failed synchronously at sites separated by up to 122 km. The overall breeding rate in 1996 at these sites was 28% (n = 201). Other instances of low breeding rate (<70%) occurred asynchronously at particular sites. We analysed variation in breeding rates to determine the contributions to annual variation of individual condition (body weight), population density, food resources and other environmental predictors. The probability of breeding declined rapidly as body condition fell below average. An index of fruitfall of hinau (Elaeocarpus dentatus), a highly nutritious food used by possums, and population density in the previous year were the most important predictors of possum condition and breeding rate. High density in the previous year coupled with low hinau fruitfall in the current year predicted below-average body condition and reduced breeding rate. Although the magnitude of these effects were only significant in ‘extreme’ years, they are consistant with delayed density-dependent effects on fecundity in brushtail possums.

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