Factors Affecting the Population Dynamics of Two Toads (Anura: Bufonidae) in a Seasonal Neotropical Savanna

Vasconcellos, Mariana M.; Colli, Guarino R.

doi:10.1643/ce-07-099

Cited by 21 publications

(24 citation statements)

References 45 publications

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“…As non‐breeders were not present at the breeding site and, therefore, were not available for capture, the ‘non‐breeder’ state was unobservable ( sensu Schaub et al. 2004; Vasconcellos & Colli 2009).…”

Section: Methodsmentioning

confidence: 99%

“…2004; Henle 2005; Bull & Carey 2009), but published reports typically focus on males or data sets where both sexes are lumped together (and are generally highly male biased). Most do not attempt to quantify temporary emigration specifically for females and the studies that present data on this phenomenon in male bufonids present divergent results, from evidence against (Vasconcellos & Colli 2009) to evidence for (Schmidt, Schaub, & Anholt 2002; Frétey et al. 2004; Muths et al.…”

Section: Introductionmentioning

confidence: 99%

“…Kuhn (1994) documented the capture of 2385 female common toads with only 329 (14%) recaptured. In a more recent, but shorter (3‐year), study of two tropical bufonids, B. schneideri and B. rubescens , Vasconcellos & Colli (2009) captured 141 males ( B. schneideri : 66, B. rubescens : 75) and 22 females ( B. schneideri : 9, B. rubescens : 13). These authors noted that 40% of the individuals for both species were only captured once but did not provide statistics specific to each sex.…”

Section: Introductionmentioning

confidence: 99%

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Unbiased survival estimates and evidence for skipped breeding opportunities in females

2010

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Summary 1.Estimates of demographic parameters for females, in many organisms, are sparse. This is particularly worrisome as more and more species are faced with high extinction probabilities and conservation increasingly depends on actions dictated by complex predictive models that require accurate estimates of demographic parameters for each sex and species. 2. This study assesses demographic parameters, specifically temporary emigration and survival, for females, a class that has been difficult to investigate historically because of lack of data. Amphibians provide a particularly good example because there is global concern about amphibian decline; yet most demographic parameter estimates are based on data from males, which we show can lead to erroneous conclusions. 3. We use 10 years of capture-recapture data from boreal toads (Bufo boreas) and the multi-state open robust design model to provide evidence for the occurrence of skipped breeding opportunities (i.e. temporary emigration) in females. This is the first time that the open robust design model has been applied to an analysis of an amphibian population that we are aware of. 4. We determined that the transition from breeder to non-breeder is obligate and the probability of a non-breeder remaining a non-breeder is 64%; thus, temporary emigration is first-order Markovian in nature, where breeding probability is dependent on the previous year's activity, i.e. if a female did not breed in year one, there is a 36% chance that she will breed in year two. With temporary emigration accounted for, we estimated between-year female survival at 87%. 5. Establishing the occurrence of temporary emigration not only reduces bias in estimates of survival probabilities but also provides information about expected breeding attempts by females, a critical element in understanding the ecology of an organism and the impacts of outside stressors and conservation actions.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unbiased survival estimates and evidence for skipped breeding opportunities in females

2010

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“…Although the POPAN approach was used by some herpetologists (e.g., Wilgers et al, 2006;Hocking and Semlitsch, 2007;Vasconcellos and Colli, 2009), its ability to estimate the total number of amphibians that use a breeding site during a season is apparently not yet widely appreciated. For example, the POPAN approach was only briefly mentioned in a recent review of population analysis methods (Mazerolle et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

The superpopulation approach for estimating the population size of 'prolonged' breeding amphibians: Examples from Europe

Wagner¹,

Pellet

Lötters

et al. 2011

Amphib Reptilia

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Individual members of a population of 'prolonged' breeding amphibian species are asynchronously present at their breeding sites. Therefore, population size estimates can be misleading when based on commonly used closed or open-population capture-mark-recapture approaches. The superpopulation approach, a modified Jolly-Seber model, has been successfully applied in taxa other than amphibians with distinct migratory behaviour and where individuals are asynchronously present at the sampling site. In this paper, we suggest that the superpopulation approach is a useful population size estimator for 'prolonged' breeding amphibian species. Two case studies on European anurans show that superpopulation estimates are much higher than simple population counts. A simulation study showed that superpopulation estimates are unbiased but that accuracy can be low when either survival or detection probabilities (or both) are low. We recommend the superpopulation approach because it matches the natural history and phenology of amphibian species with prolonged breeding seasons.

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“…Despite this, little is known of the ecology of the species, which is considered to be a habitat generalist with a preference for open vegetation (Silvano and Pimenta, 2003;Vasconcellos and Colli, 2009;Batista et al, 2011). Widely distributed and abundant species such as R. schneideri are generally the most appropriate models for the investigation of the effects of habitat loss and fragmentation (Whiteley, Spruell and Allendorf, 2006).…”

Section: Introductionmentioning

confidence: 99%

Contemporary gene flow and weak genetic structuring in Rococo toad (Rhinella schneideri) populations in habitats fragmented by agricultural activities

et al. 2011

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The reduced vagility and philopatric behaviour of most amphibians make them especially vulnerable to the effects of habitat fragmentation, in particular the loss of genetic variation. However, almost no data are available on the effects of agricultural practices on populations of Neotropical amphibians. Here, the genetic diversity of Rococo toad (Rhinella schneideri) populations in the highly disturbed landscape of the north-western region of the Brazilian state of São Paulo was analysed using microsatellite markers. Two areas were sampled -one dominated by open pastures (four populations) and the other by sugar cane plantations (two populations) -in an attempt to evaluate the possible influence of the type of anthropogenic matrix on genetic variability and gene flow (dispersion). The populations presented a relatively uniform genetic stock, with low levels of inbreeding (Fis) and high levels of admixture between localities (Fst, Rst, STRUCTURE) indicating no genetic subdivision. The results indicated relatively high levels of recent migration among sites (m) and no isolation by distance. The analyses also found that historical and contemporary rates of migration among populations were broadly similar. Overall, then, neither type of matrix appeared to have an effect on the connectivity of the Rococo toad populations. This suggests that the species has a considerable capacity for dispersal, allowing it to maintain a relatively homogeneous population, even under intense human pressure.

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Factors Affecting the Population Dynamics of Two Toads (Anura: Bufonidae) in a Seasonal Neotropical Savanna

Cited by 21 publications

References 45 publications

Unbiased survival estimates and evidence for skipped breeding opportunities in females

Unbiased survival estimates and evidence for skipped breeding opportunities in females

The superpopulation approach for estimating the population size of 'prolonged' breeding amphibians: Examples from Europe

Contemporary gene flow and weak genetic structuring in Rococo toad (Rhinella schneideri) populations in habitats fragmented by agricultural activities

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