Biology subjects

Fitzpatrick, S. W.

Publications and source records attributed to Fitzpatrick, S. W..

6 recordsLinked to original sources

bioRxiv2024

Whole-genome sequencing across space and time reveals impact of population decline and reduced gene flow in Florida Scrub-Jays

Whole-genome sequence data is proving to be highly informative about the past demography of free-living populations, and in the context of endangered species, it can provide a quantification of the genetic risk posed by reduced genetic diversity and inbreeding. Prior to 1920, the Florida scrub-jay (Aphelocoma coerulescens) had been widespread across Florida, but with the expansion of agriculture and human habitation, its population has declined by 95%, resulting in fragmentation into semi-isolated subpopulations. By sequencing 241 individuals sampled from five different regions and across two time points, this study quantifies a greater magnitude of loss of genetic diversity and greater levels of inbreeding in smaller and more isolated subpopulations. Consistent with population genetics theory, reduction in population size results in a dramatic loss of rare alleles, skewing the site frequency spectrum far from the expected equilibrium. Increased inbreeding in the smaller, more remote subpopulations is especially evident in the increased size and number of runs of homozygosity. The Florida scrub-jay displays limited dispersal, and habitat fragmentation has greatly reduced the magnitude of gene flow in the past 30 years, resulting in further decline of genetic diversity, especially in the peripheral populations. Analysis of these data is informative in guiding conservation efforts to retain genetic diversity and minimize the consequences of inbreeding in the Florida scrub-jay. HighlightsO_LIFive regional populations show distinct degrees of population isolation and decline. C_LIO_LIThere has been commensurate loss of genetic diversity, skewed site frequency spectra, reduced migration, and increased inbreeding (FROH). C_LIO_LIAs many state-wide populations decline, the smaller, more remote populations provide a glimpse into the future and a testbed for remediation approaches. C_LI

genomics↗

bioRxiv2024

Pitfalls and windfalls of detecting demographic declines using population genetics in long-lived species

Detecting recent demographic changes is a crucial component of species conservation and management, as many natural populations face declines due to anthropogenic habitat alteration and climate change. Genetic methods allow researchers to detect changes in effective population size (Ne) from sampling at a single timepoint. However, in species with long lifespans, there is a lag between the start of a decline in a population and the resulting decrease in genetic diversity. This lag slows the rate at which diversity is lost, and therefore makes it difficult to detect recent declines using genetic data. However, the genomes of old individuals can provide a window into the past, and can be compared to those of younger individuals, a contrast that may help reveal recent demographic declines. To test whether comparing the genomes of young and old individuals can help infer recent demographic bottlenecks, we use forward-time, individual-based simulations with varying mean individual lifespans and extents of generational overlap. We find that age information can be used to aid in the detection of demographic declines when the decline has been severe. When average lifespan is long, comparing young and old individuals from a single timepoint has greater power to detect a recent (within the last 50 years) bottleneck event than comparing individuals sampled at different points in time. Our results demonstrate how longevity and generational overlap can be both a hindrance and a boon to detecting recent demographic declines from population genomic data.

evolutionary biology↗

bioRxiv2023

Translocations spur population growth but exacerbate inbreeding in an imperiled species

Land and natural resource usage that supports human society can pose a risk to the survival of other species, spurring biodiversity loss. In extreme cases, when development threatens the existence of individuals, wildlife managers may perform mitigation translocations, relocating individuals out of harms way. We investigated the efficacy of mitigation translocations as a conservation strategy in Federally Threatened Florida Scrub-Jays using a dataset that provided unprecedented resolution into both the demographic and genomic outcomes of translocations. Over the course of seven years, a total of fourteen groups (51 jays) from five subpopulations that had been declining from agriculture and lack-of-fire driven habitat degradation were translocated to a larger site of more contiguous restored habitat with only four family groups, to mitigate for loss of these subpopulations from mining activity. Habitat restoration and translocations established a core population that increased 10-fold in size after only 17 years from the first translocations. Pedigree analyses of this population revealed that a small subset of mostly translocated individuals fueled the demographic expansion, with a single breeding pair responsible for [~]24% of the ancestral genetic contributions since 2008. Genomic comparisons between translocated individuals and individuals from the core population before and after translocations revealed that the high reproductive skew led to increased inbreeding and loss of genetic diversity. This study stresses the importance of demographic and genetic monitoring following translocations, and that subsequent, genetic-rescue-oriented translocations may be necessary in mitigation scenarios to counter the genetic consequences of reproductive skew in fragmented populations. Significance StatementThere is ongoing debate surrounding the effectiveness of mitigation-driven translocations for conservation, however we show that translocations to mitigate the effects of mining on Federally Threatened Florida Scrub-Jays spurred population growth; a major boon to the viability of this species. We translocated individuals from at-risk subpopulations that were demographic sinks into recently restored habitat, which quickly established a rapidly growing core population. We demonstrate that demographic and genetic recovery do not necessarily go hand-in-hand, as reproduction was highly skewed towards a small subset of mostly translocated individuals, which increased inbreeding and eroded genetic diversity. This stresses the importance of demographic and genetic monitoring for identifying reproductive skew, allowing for adaptive management that addresses inbreeding and achieves broader conservation goals.

evolutionary biology↗

bioRxiv2021

The crucial role of genome-wide genetic variation in conservation

The unprecedented rate of extinction calls for efficient use of genetics to help conserve biodiversity. Several recent genomic and simulation-based studies have argued that the field of conservation biology has placed too much focus on the conservation of genome-wide genetic variation, and that this approach should be replaced with another that focuses instead on managing the subset of functional genetic variation that is thought to affect fitness. Here, we critically evaluate the feasibility and likely benefits of this approach in conservation. We find that population genetics theory and empirical results show that the conserving genome-wide genetic variation is generally the best approach to prevent inbreeding depression and loss of adaptive potential from driving populations towards extinction. Focusing conservation efforts on presumably functional genetic variation will only be feasible occasionally, often misleading, and counterproductive when prioritized over genome-wide genetic variation. Given the increasing rate of habitat loss and other environmental changes, failure to recognize the detrimental effects of lost genome-wide variation on long-term population viability will only worsen the biodiversity crisis.

evolutionary biology↗

bioRxiv2020

Rapture-ready darters: sequence capture outperforms whole genome data regardless of reference genome in Etheostoma

Researchers studying non-model organisms have an increasing number of methods available for generating genomic data. However, the applicability of different methods across species, as well as the effect of reference genome choice on population genomic inference, are still difficult to predict in many cases. We evaluated the impact of data type (whole-genome vs. reduced representation) and reference genome choice on data quality and on population genomic and phylogenomic inference across several species of darters (subfamily Etheostomatinae), a highly diverse radiation of freshwater fish. We generated a high-quality reference genome and developed a hybrid RADseq/sequence capture (Rapture) protocol for the Arkansas darter (Etheostoma cragini). Rapture data from 1900 individuals spanning four darter species showed recovery of most loci across darter species at high depth and consistent estimates of heterozygosity regardless of reference genome choice. Loci with baits spanning both sides of the restriction enzyme cut site performed especially well across species. For low-coverage whole-genome data, choice of reference genome affected read depth and inferred heterozygosity. For similar amounts of sequence data, Rapture performed better at identifying fine-scale genetic structure compared to whole-genome sequencing. Rapture loci also recovered an accurate phylogeny for the study species and demonstrated high phylogenetic informativeness across the evolutionary history of the genus Etheostoma. Low cost and high cross-species effectiveness regardless of reference genome suggest that Rapture and similar sequence capture methods may be worthwhile choices for studies of diverse species radiations.

genomics↗

bioRxiv2019

Genetic rescue without genomic swamping in wild populations

Gene flow is an enigmatic evolutionary force because it can limit adaptation but can also help populations escape inbreeding depression. Manipulating gene flow for conservation purposes is a controversial, but potentially powerful management strategy. We use multigenerational pedigrees and genomics to test demographic and evolutionary consequences of manipulating gene flow in two isolated wild Trinidadian guppy populations. We found that on average, hybrids lived longer and reproduced more. Despite overall genome-wide homogenization, alleles potentially associated with local adaptation were not entirely swamped by gene flow. Our results suggest that combining new genomic variation from immigrants with potentially adaptive variation from the recipient population resulted in highly fit hybrids and subsequent increases in population size. Contrary to the prevailing view that gene flow constrains adaptation, our study shows that immigration can produce long-term fitness benefits in small populations without swamping locally adaptive variation.

evolutionary biology↗