Fires slow population declines of a long-lived prairie plant through multiple vital rates

Large-scale habitat loss is frequently identified with loss of biodiversity, but examples of the direct effect of habitat alterations on changes in vital rates remain rare. Quantifying and understanding the relationship between habitat composition and changes in vital rates, however, is essential for the development of effective conservation strategies. It has been suggested that the decline of woodland caribou Rangifer tarandus caribou populations in North America is precipitated by timber harvesting that creates landscapes of early seral forests. Such habitat changes have altered the predator-prey system resulting in asymmetric predation, where predators are maintained by alternative prey (i.e. apparent competition). However, a direct link between habitat condition and caribou population declines has not been documented. We estimated survival probabilities for the threatened arboreal lichen-feeding ecotype of woodland caribou in British Columbia, Canada, at two different spatial scales. At the broader scale, observed variation in adult female survival rates among 10 distinct populations (range = 0.67-0.93) was best explained by variation in the amount of early seral stands within population ranges and population density. At the finer scale, home ranges of caribou killed by predators had lower proportions of old forest and more mid-aged forest as compared with multi-annual home ranges where caribou were alive. These results are consistent with predictions from the apparent competition hypothesis and quantify direct fitness consequences for caribou following habitat alterations. We conclude that apparent competition can cause rapid population declines and even extinction where changes in species composition occur following large scale habitat change. © 2007 The Authors. Journal compilation © 2007 British Ecological Society.

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A novel approach to compare pinniped populations across a broad geographic range

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2014-0070 ◽

2015 ◽

Vol 72 (2) ◽

pp. 175-185 ◽

Cited By ~ 11

Author(s):

Kathryn L. Sweeney ◽

Kyle W. Shertzer ◽

Lowell W. Fritz ◽

Andrew J. Read

Keyword(s):

Geographic Range ◽

Aerial Images ◽

Distribution Model ◽

Vital Rates ◽

Adult Males ◽

Population Declines ◽

Sea Lions ◽

Adult Females ◽

Broad Region ◽

Site Types

We utilized aerial images and employed photogrammetric methodologies to collect standardized lengths of Steller sea lions (Eumetopias jubatus) terrestrially hauled out. We conducted comparisons among all site types and separately for rookery and haulout site-types between the two distinct population segments (DPSs; eastern and western) and two broad regions within the western DPS experiencing contrasting population abundance trends. An observed adult female index was created from measurements of reproductive females — in the presence of a pup or juvenile — and was applied as a model constraint for “adult females”. We fitted a finite mixture distribution model to the length-frequency data to estimate the proportion population for three delineated age–sex classes (juveniles, adult females, and adult males) and mean length for juveniles and adult males. Estimated proportions reflected what we expected; however, the broad region within the western DPS exhibiting substantial population declines had greater proportion of all age–sex classes on rookery sites than increasing broad region. Adult sea lions were significantly shorter in the eastern DPS than the western area, providing further evidence of morphological differences between the DPSs. We also introduce a less resource-demanding method for estimating population demographics, and potentially vital rates, for pinnipeds across a vast geographic range.

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Demographic compensation does not rescue populations at a trailing range edge

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1715899115 ◽

2018 ◽

Vol 115 (10) ◽

pp. 2413-2418 ◽

Cited By ~ 29

Author(s):

Seema Nayan Sheth ◽

Amy Lauren Angert

Keyword(s):

Environmental Gradients ◽

Demographic Data ◽

Species Range ◽

Severe Drought ◽

Vital Rates ◽

Population Declines ◽

Geographic Ranges ◽

Population Growth Rates ◽

Range Edge ◽

Outstanding Question

Species’ geographic ranges and climatic niches are likely to be increasingly mismatched due to rapid climate change. If a species’ range and niche are out of equilibrium, then population performance should decrease from high-latitude “leading” range edges, where populations are expanding into recently ameliorated habitats, to low-latitude “trailing” range edges, where populations are contracting from newly unsuitable areas. Demographic compensation is a phenomenon whereby declines in some vital rates are offset by increases in others across time or space. In theory, demographic compensation could increase the range of environments over which populations can succeed and forestall range contraction at trailing edges. An outstanding question is whether range limits and range contractions reflect inadequate demographic compensation across environmental gradients, causing population declines at range edges. We collected demographic data from 32 populations of the scarlet monkeyflower (Erythranthe cardinalis) spanning 11° of latitude in western North America and used integral projection models to evaluate population dynamics and assess demographic compensation across the species’ range. During the 5-y study period, which included multiple years of severe drought and warming, population growth rates decreased from north to south, consistent with leading-trailing dynamics. Southern populations at the trailing range edge declined due to reduced survival, growth, and recruitment, despite compensatory increases in reproduction and faster life-history characteristics. These results suggest that demographic compensation may only delay population collapse without the return of more favorable conditions or the contribution of other buffering mechanisms such as evolutionary rescue.

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Growing as slow as a turtle: Unexpected maturational differences in a small, long-lived species

PLoS ONE ◽

10.1371/journal.pone.0259978 ◽

2021 ◽

Vol 16 (11) ◽

pp. e0259978

Author(s):

Devin Edmonds ◽

Michael J. Dreslik ◽

Jeffrey E. Lovich ◽

Thomas P. Wilson ◽

Carl H. Ernst

Keyword(s):

Growth Rate ◽

Growth Model ◽

Life History Theory ◽

Demographic Data ◽

Strong Support ◽

Rate Variation ◽

Vital Rates ◽

Population Declines ◽

Mark Recapture ◽

Adult Growth

Turtle body size is associated with demographic and other traits like mating success, reproductive output, maturity, and survival. As such, growth analyses are valuable for testing life history theory, demographic modeling, and conservation planning. Two important but unsettled research areas relate to growth after maturity and growth rate variation. If individuals exhibit indeterminate growth after maturity, older adults may have an advantage in fecundity, survival, or both over younger/smaller adults. Similarly, depending on how growth varies, a portion of the population may mature earlier, grow larger, or both. We used 23-years of capture-mark-recapture data to study growth and maturity in the Spotted Turtle (Clemmys guttata), a species suffering severe population declines and for which demographic data are needed for development of effective conservation and management strategies. There was strong support for models incorporating sex as a factor, with the interval growth model reparametrized for capture-mark-recapture data producing later mean maturation estimates than the age-based growth model. We found most individuals (94%) continued growing after maturity, but the instantaneous relative annual plastral growth rate was low. We recommend future studies examine the possible contribution of such slow, continued adult growth to fecundity and survival. Even seemingly negligible amounts of annual adult growth can have demographic consequences affecting the population vital rates for long-lived species.

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Occupation-Specific Population Models: Population and Dynastic Cycles

Population Dynamics ◽

10.1093/oso/9780195121582.003.0014 ◽

1998 ◽

Author(s):

C. Y. Cyrus Chu

Keyword(s):

Population Dynamics ◽

Population Decline ◽

Population Data ◽

Chinese History ◽

Vital Rates ◽

Population Declines ◽

Chinese Populations ◽

Biological Responses ◽

Density Dependency ◽

In The Beginning

As Lee (1987) pointed out, vital rates of the human population are often determined by forces such as culture, institutions, technology, and individual rationality, forces that have little to do with density pressure or prior growth. Perhaps most people also expect “rational” human practice to weaken the biological responses of both fertility and mortality to density pressure, while strengthening the nonbiological response through institutional regulations. But can human institutional designs and rational responses really reduce the impact of natural checks? As we study the pattern of population dynamics in ancient China, we can provide some viewpoints different from the general opinion. The long-term relationship between human institutional designs and natural checks is discussed in chapter 14. The books by Ho (1959) and Chao and Hsieh (1988; hereinafter C&H) contain the most thorough research on the history of Chinese population. The data summarized in C&H have presented us with a time-population diagram, shown in figure 9.1. From this figure, as well as other related literature, the following “stylized facts” of population dynamics in Chinese history can be summarized: 1. Population declines often coincided with dynasty changes (C&H; Ho, 1959). 2. Population declines were often drastic in a rather short period of time. 3. Natural checks such as famine and epidemics did not independently reduce the population surplus (Ho, 1959); rather, population declines were often the direct and indirect results of internecine wars. 4. There are obvious peaks and troughs in the population data, but no regular cyclical patterns (C&H). The fact that no serious population decline appears to have been independently due to famines and epidemics seems to suggest a weak pattern of density-dependency for ancient Chinese populations, a pattern consistent with the observation of Lee mentioned in the beginning of this chapter. However, as noted by many historians (see, e.g., Ho, 1959, and C&H 1988), the frequent clashes between soldiers and rebellious peasants in Chinese history were often initiated by famine or density pressure. As such, the originally weak natural checks on population were often magnified by war, and such magnified “institutional checks” caused very drastic population changes.

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Variable vital rates and the risk of population declines in Adélie penguins from the Antarctic Peninsula region

Ecosphere ◽

10.1002/ecs2.1666 ◽

2017 ◽

Vol 8 (1) ◽

pp. e01666 ◽

Cited By ~ 8

Author(s):

Jefferson T. Hinke ◽

Susan G. Trivelpiece ◽

Wayne Z. Trivelpiece

Keyword(s):

Antarctic Peninsula ◽

Vital Rates ◽

Population Declines ◽

The Antarctic ◽

Adélie Penguins

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Changes in landscape composition influence the decline of a threatened woodland caribou population

10.26686/wgtn.12971855.v1 ◽

2020 ◽

Author(s):

Heiko Wittmer ◽

B McLellan ◽

R Serrouya ◽

C Apps

Keyword(s):

Large Scale ◽

Spatial Scales ◽

Apparent Competition ◽

Timber Harvesting ◽

Conservation Strategies ◽

Home Ranges ◽

Vital Rates ◽

Population Declines ◽

Woodland Caribou ◽

Habitat Alterations

Large-scale habitat loss is frequently identified with loss of biodiversity, but examples of the direct effect of habitat alterations on changes in vital rates remain rare. Quantifying and understanding the relationship between habitat composition and changes in vital rates, however, is essential for the development of effective conservation strategies. It has been suggested that the decline of woodland caribou Rangifer tarandus caribou populations in North America is precipitated by timber harvesting that creates landscapes of early seral forests. Such habitat changes have altered the predator-prey system resulting in asymmetric predation, where predators are maintained by alternative prey (i.e. apparent competition). However, a direct link between habitat condition and caribou population declines has not been documented. We estimated survival probabilities for the threatened arboreal lichen-feeding ecotype of woodland caribou in British Columbia, Canada, at two different spatial scales. At the broader scale, observed variation in adult female survival rates among 10 distinct populations (range = 0.67-0.93) was best explained by variation in the amount of early seral stands within population ranges and population density. At the finer scale, home ranges of caribou killed by predators had lower proportions of old forest and more mid-aged forest as compared with multi-annual home ranges where caribou were alive. These results are consistent with predictions from the apparent competition hypothesis and quantify direct fitness consequences for caribou following habitat alterations. We conclude that apparent competition can cause rapid population declines and even extinction where changes in species composition occur following large scale habitat change. © 2007 The Authors. Journal compilation © 2007 British Ecological Society.

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A Long-Term Demographic Analysis of Spotted Turtles (Clemmys guttata) in Illinois Using Matrix Models

Diversity ◽

10.3390/d11120226 ◽

2019 ◽

Vol 11 (12) ◽

pp. 226

Author(s):

Christina Y. Feng ◽

Jason P. Ross ◽

David Mauger ◽

Michael J. Dreslik

Keyword(s):

Population Growth ◽

Matrix Models ◽

Habitat Management ◽

Adult Survival ◽

Vital Rates ◽

Population Declines ◽

Mark Recapture ◽

Adult Age ◽

Clemmys Guttata ◽

Spotted Turtle

Matrix models and perturbation analyses provide a useful framework for evaluating demographic vital rates crucial to maintaining population growth. Determining which vital rates most influence population growth is necessary for effective management of long-lived organisms facing population declines. In Illinois, the state-endangered Spotted Turtle (Clemmys guttata) occurs in two distinct populations, and management can benefit from an understanding of its demographic behavior. We conducted a mark–recapture study on both populations in 2015 and 2016 and used historical mark–recapture data from 1988 to 2010 to determine female age-specific survival and fecundity rates. Survival increased significantly with age, and age-specific reproductive output and fecundity were >1.0. However, both populations exhibited net reproductive rates below replacement levels, and one population had a negative growth rate. Summed elasticities for all adult age classes indicate adult survival has the highest proportional impact on population growth. We found evidence of demographic divergence between the two populations, and thus the prioritization of vital rates varied somewhat between sites, with a relatively higher emphasis on juvenile and young adult survival for one population. We recommend conservation actions such as habitat management and predator control, which will have positive impacts across stage classes.

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No evidence of a demographic response to experimental herbicide treatments by the White-crowned Sparrow, an early successional forest songbird

The Condor ◽

10.1093/condor/duz004 ◽

2019 ◽

Vol 121 (2) ◽

Author(s):

James W Rivers ◽

Jake Verschuyl ◽

Carl J Schwarz ◽

Andrew J Kroll ◽

Matthew G Betts

Keyword(s):

Pacific Northwest ◽

Large Scale ◽

Nest Survival ◽

Control Measures ◽

Vital Rates ◽

Population Declines ◽

Vegetative Cover ◽

Vegetation Control ◽

Herbicide Treatments ◽

Demographic Response

Abstract Early-successional forest birds, which depend on disturbance events within forested landscapes, have received increased conservation concern because of long-term population declines. Herbicides are often used to control vegetation within early-successional forests, with unknown effects on avian vital rates. We used a large-scale experiment to test how nest and post-fledging survival were influenced by herbicide intensity within managed conifer plantations across 2 breeding seasons. We created a gradient of 4 stand-scale herbicide treatments (light, moderate, and intensive, and no-spray control) and evaluated the reproductive response of the White-crowned Sparrow (Zonotrichia leucophrys), a declining songbird in managed forest landscapes of the Pacific Northwest. Against initial predictions, we found no evidence that either daily nest survival (n > 760 nests across all treatments) or post-fledging survival (n = 70 individuals reared in control and moderate treatments) were influenced by herbicide application intensity. Increased herbicide intensity resulted in an extensive reduction in vegetation cover at both stand and nest-patch scales; in contrast, vegetative cover at nest sites did not differ across herbicide treatments, nor was nest survival related to vegetation concealment measures. As the largest experimental investigation to assess forest herbicide effects on songbird demography, our study indicates that components of sparrow reproductive success were not influenced by experimental vegetation control measures, although additional work on other early-successional species will be useful to evaluate the generalities of our findings.

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Life-History Variation and Demography in Western Bluebirds (Sialia Mexicana) in Oregon

The Auk ◽

10.1093/auk/121.1.118 ◽

2004 ◽

Vol 121 (1) ◽

pp. 118-133

Author(s):

Amber J. Keyser ◽

Marilynne T. Keyser ◽

Daniel E. L. Promislow

Keyword(s):

Conservation Status ◽

Vital Rates ◽

Adult Males ◽

Population Declines ◽

Life History Variation ◽

Data Set ◽

Sialia Mexicana ◽

Demographic Processes ◽

Western Bluebirds ◽

Using Data

Abstract During the seven-year period from 1995 to 2001, we conducted a detailed, demographic study of a population of Western Bluebirds (Sialia mexicana) in Oregon. Using a data set consisting of individual capture histories for ≈8,000 birds, we estimated age-specific and study-year specific survival estimates of adult males and females. High juvenile recruitment enabled us to generate accurate estimates of juvenile survival from fledging to first breeding attempt. We analyzed fecundity patterns, including nesting phenology, clutch success, and overall reproductive success for nearly 1,200 nesting attempts. Temporal variation in survival and fecundity had strong demographic consequences. Asymptotic population growth analysis suggested a slowly growing population. However, variation in vital rates led to population declines even over the relative short timescale of our study, making the conservation status of this species uncertain. In addition to those results, we discuss the costs and benefits of using data collected by volunteers to study demographic processes.

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