Demography and genetics suggest reversal of dolphin source‐sink dynamics, with implications for conservation

Manlik, Oliver; Chabanne, D.; Daniel, Claire; Bejder, Lars; Allen, S. J.; Sherwin, William B.

doi:10.1111/mms.12555

Cited by 23 publications

(25 citation statements)

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“…Adult females in the inner estuary of the Gulf of Guayaquil have higher residence level and smaller home ranges than males (Félix et al, 2019a), which has also been observed in other bottlenose populations elsewhere (Wells et al, 1987;Möller and Beheregaray, 2004;Sprogis et al, 2015). However, higher dispersal rate by females has been reported in bottlenose dolphins in Scotland (Natoli et al, 2005) and in the Indo-Pacific bottlenose dolphin from Western Australia (Manlik et al, 2019), apparently driven by habitat quality, hence selective emigration cannot be ruled out as a potential explanation to what occurred with these two dolphin communities in our study area.…”

Section: Discussionsupporting

confidence: 55%

Imminent Risk of Extirpation for Two Bottlenose Dolphin Communities in the Gulf of Guayaquil, Ecuador

Félix

Burneo

2020

Front. Mar. Sci.

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A long-term study of a common bottlenose dolphin (Tursiops truncatus) population inhabiting the Gulf of Guayaquil, Ecuador (2 • 33 S, 79 • 20 W), has been carried out for almost 30 years. Similarly, as in other parts of the world, this population is structured socially and spatially in well-defined subunits or communities. Two of these communities, referred to as Posorja and El Morro, have been studied with major intensity in the last 10 years in the western inner estuary, among others to calculate population parameters that allow assessing their viability in time. Calculated parameters include annual abundance, age and sex composition, annual crude birth rate, calf survival, calf production interval, and average annual mortality/emigration. With these parameters and others derived from other better-studied populations, the trend of both subunits was modeled using the software Vortex. Results show that even under an optimistic scenery both communities will be extinct in the short (Posorja) and mid-term (El Morro), if current stressors continue. Most population parameters calculated in both communities show similar values as in populations elsewhere, but a very low calf survival in Posorja and high mortality/emigration ratios in adults, and probably in juveniles in both communities, contribute to this trend. Population deterioration seems to be the result of different human-induced threats such as fisheries, maritime traffic and others still not well assessed, as well as stochastic demographic events. We recommend taking actions in the short term to halt population decline addressing the major causes of mortality affecting these dolphin communities.

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Section: Discussionsupporting

confidence: 55%

Imminent Risk of Extirpation for Two Bottlenose Dolphin Communities in the Gulf of Guayaquil, Ecuador

Félix

Burneo

2020

Front. Mar. Sci.

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“… Microsatellite diversity measures based on the BB maximum sampling approach are from Manlik et al (). …”

Section: Resultsmentioning

confidence: 99%

“… MHC DNA sequence alignment available in Dryad/Figure (Manlik et al, ; https://doi.org/10.5061/dryad.73k278d). Microsatellite data: previously uploaded in supplement of published article (Manlik et al, ): https://doi.org/10.1111/mms.12555. Additional microsatellite data now in Dryad/Table , available from the Dryad Digital Repository: Manlik et al () https://doi.org/10.5061/dryad.73k278d. Various other data available in Dryad/Appendix ( https://doi.org/10.5061/dryad.73k278d; Manlik et al, ), including: conservative sampling design and numbers (Table ), MHC and microsatellite diversity measures, including F ST (Table ), BLASTN results (Table ), diversity measures and statistics for microsatellite subsamples (Table ). …”

Section: Data Accessibilitymentioning

confidence: 99%

Is MHC diversity a better marker for conservation than neutral genetic diversity? A case study of two contrasting dolphin populations

Manlik

Krützen

Kopps

et al. 2019

Ecology and Evolution

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Genetic diversity is essential for populations to adapt to changing environments. Measures of genetic diversity are often based on selectively neutral markers, such as microsatellites. Genetic diversity to guide conservation management, however, is better reflected by adaptive markers, including genes of the major histocompatibility complex (MHC). Our aim was to assess MHC and neutral genetic diversity in two contrasting bottlenose dolphin (Tursiops aduncus) populations in Western Australia—one apparently viable population with high reproductive output (Shark Bay) and one with lower reproductive output that was forecast to decline (Bunbury). We assessed genetic variation in the two populations by sequencing the MHC class II DQB, which encompasses the functionally important peptide binding regions (PBR). Neutral genetic diversity was assessed by genotyping twenty‐three microsatellite loci. We confirmed that MHC is an adaptive marker in both populations. Overall, the Shark Bay population exhibited greater MHC diversity than the Bunbury population—for example, it displayed greater MHC nucleotide diversity. In contrast, the difference in microsatellite diversity between the two populations was comparatively low. Our findings are consistent with the hypothesis that viable populations typically display greater genetic diversity than less viable populations. The results also suggest that MHC variation is more closely associated with population viability than neutral genetic variation. Although the inferences from our findings are limited, because we only compared two populations, our results add to a growing number of studies that highlight the usefulness of MHC as a potentially suitable genetic marker for animal conservation. The Shark Bay population, which carries greater adaptive genetic diversity than the Bunbury population, is thus likely more robust to natural or human‐induced changes to the coastal ecosystem it inhabits.

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“…Low reproductive rates have been identified as the leading cause for the decline (Manlik et al., ). Historically, the Bunbury dolphin population has served as a “source” population for the larger meta‐population along the southwestern Australian coast (Manlik et al., In Press), and more recently, the abundance and temporary emigration of the population are also influenced by climate variability (Sprogis, Christiansen, Wandres, & Bejder, ), thus raising additional conservation concerns for the overall meta‐population viability. Therefore, it is important to understand both the ability to detect trends in population abundance and to quantify demographic parameters for this population to best inform management.…”

Section: Introductionmentioning

confidence: 99%

Implications of survey effort on estimating demographic parameters of a long‐lived marine top predator

Symons

Sprogis

Bejder

2018

Ecology and Evolution

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Effective management of wildlife populations rely on knowledge of their abundance, survival, and reproductive rates. Maintaining long‐term studies capable of estimating demographic parameters for long‐lived, slow‐reproducing species is challenging. Insights into the effects of research intensity on the statistical power to estimate demographic parameters are limited. Here, we investigate implications of survey effort on estimating abundance, home range sizes, and reproductive output of Indo‐Pacific bottlenose dolphins (Tursiops aduncus), using a 3‐year subsample of a long‐term, capture–recapture study off Bunbury, Western Australia. Photo‐identification on individual dolphins was collected following Pollock's Robust Design, where seasons were defined as “primary periods”, each consisting of multiple “secondary periods.” The full dataset consisted of 12 primary periods and 72 secondary periods, resulting in the study area being surveyed 24 times/year. We simulated reduced survey effort by randomly removing one, two, or three secondary periods per primary period. Capture–recapture models were used to assess the effect of survey intensity on the power to detect trends in population abundance, while individual dolphin sighting histories were used to assess the ability to conduct home range analyses. We used sighting records of adult females and their calving histories to assess survey effort on quantifying reproductive output. A 50% reduction in survey effort resulted in (a) up to a 36% decline in population abundance at the time of detection; (b) a reduced ability to estimate home range sizes, by increasing the time for individuals to be sighted on ≥30 occasions (an often‐used metric for home range analyses) from 7.74 to 14.32 years; and (c) 33%, 24%, and 33% of annual calving events across three years going undocumented, respectively. Results clearly illustrate the importance of survey effort on the ability to assess demographic parameters with clear implications for population viability analyses, population forecasting, and conservation efforts to manage human–wildlife interactions.

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Demography and genetics suggest reversal of dolphin source‐sink dynamics, with implications for conservation

Cited by 23 publications

References 91 publications

Imminent Risk of Extirpation for Two Bottlenose Dolphin Communities in the Gulf of Guayaquil, Ecuador

Imminent Risk of Extirpation for Two Bottlenose Dolphin Communities in the Gulf of Guayaquil, Ecuador

Is MHC diversity a better marker for conservation than neutral genetic diversity? A case study of two contrasting dolphin populations

Implications of survey effort on estimating demographic parameters of a long‐lived marine top predator

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