Zachery Wells | St Francis Xavier University (Nova Scotia, Canada) (original) (raw)

Papers by Zachery Wells

Files associated with the MacroPopGenBase: 1) .XLSX file documenting references for asso... more Files associated with the MacroPopGenBase: 1) .XLSX file documenting references for associated reference IDs, and list of key terms used in meta-analytical searches. 2) .XLSX with MacroPopGenBase data [24 columns, 9090 rows] as well as data file documenting all localities and distances between them [26 columns, 10921 rows]. Associated Read Me tabs also included.***** Current version: v0.2, June 24, 2020 **** 3) .CSV file with subset of North American mammal data used for testing ascertainment bias associated with mirosatellite loci. 4) All R code used to produce figures and analyses presented in Lawrence et al. (in revision) Scientific Data

As a population’s genetic makeup is often attributed to the combined fitness of its individuals, ... more As a population’s genetic makeup is often attributed to the combined fitness of its individuals, the adoption of deliberate hybridization practices is an area of interest for many hatchery and conservation programs. Using a common garden experimental design involving eight wild populations of Salvelinus fontinalis (brook trout), we studied how effective population size (Ne), divergence (QST, km), and environmental dissimilarity (pH, temperature) may influence hybridization outcomes for fitness related traits under moderate climate warming. Additionally, we looked at the ability of six of these populations to tolerate acute thermal warming, and whether or not this tolerance could be altered by hybridizing populations. Critical thermal maximum (CTmax) assays were conducted on juveniles from each population to assess thermal tolerance, and agitation temperature (a behavioural metric quantifying temperature at the onset of refugia-seeking behaviour) was recorded for assessing behavioura...

Scientific Data, Apr 3, 2019

Population genetic data from nuclear DNa has yet to be synthesized to allow broad scale compariso... more Population genetic data from nuclear DNa has yet to be synthesized to allow broad scale comparisons of intraspecific diversity versus species diversity. The MacroPopGen database collates and georeferences vertebrate population genetic data across the Americas from 1,308 nuclear microsatellite DNA studies, 897 species, and 9,090 genetically distinct populations where genetic differentiation (F St) was measured. Caribbean populations were particularly distinguished from North, Central, and South American populations, in having higher differentiation (F St = 0.12 vs. 0.07-0.09) and lower mean numbers of alleles (MNa = 4.11 vs. 4.84-5.54). While mammalian populations had lower MNA (4.86) than anadromous fish, reptiles, amphibians, freshwater fish, and birds (5.34-7.81), mean heterozygosity was largely similar across groups (0.57-0.63). Mean F St was consistently lowest in anadromous fishes (0.06) and birds (0.05) relative to all other groups (0.09-0.11). Significant differences in Family/Genera variance among continental regions or taxonomic groups were also observed. MacroPopGen can be used in many future applications including latitudinal analyses, spatial analyses (e.g. central-margin), taxonomic comparisons, regional assessments of anthropogenic impacts on biodiversity, and conservation of wild populations.

Conservation Genetics

Although hybridization can be used as a tool for genetic rescue, it can also generate outbreeding... more Although hybridization can be used as a tool for genetic rescue, it can also generate outbreeding depression and reduce local adaptation. Improved understanding of these processes is required to better inform conservation decisions for threatened populations. Few studies, however, investigate how multiple factors influence hybridization effects. We investigated how effective population sizes (Ne), geographic distance, genetic divergence (QST, FST), and environmental stress influence hybridization effects among eight highly divergent brook trout (Salvelinus fontinalis) populations varying in Ne (range 44–589). In a common garden, we compared three fitness-related traits among hybrid and non-hybrid crosses. Contrary to expectations, we found little evidence of outbreeding depression; instead, hybridization effects were mostly neutral (60/66 non-hybrid vs. hybrid comparisons) with some support for heterosis (6/66). When controlling for maternal-family effects, several factors influenced fitness-related traits but cumulatively explained little variance in relative hybrid fitness (0–6.4%). For instance, when hybridized dams came from small Ne populations, relative fitness increased for some traits (length at hatch), suggesting heterosis, yet decreased at other traits (survival to hatch), suggesting outbreeding depression. Trait inconsistencies in relative hybrid fitness were also observed under different degrees of environmental stress. Results also differed when family variance in hybridization effects was unaccounted for. Collectively, our results suggest that, under certain conditions, current guidelines on genetic rescue and associated outbreeding risks might be too conservative. The occurrence of genetic rescue and outbreeding depression, nonetheless, remain difficult to predict because families and individual traits can express different effects from hybridization within populations.

Conservation Physiology, 2016

As climate warming threatens the persistence of many species and populations, it is important to ... more As climate warming threatens the persistence of many species and populations, it is important to forecast their responses to warming thermal regimes. Climate warming often traps populations in smaller habitat fragments, not only changing biotic parameters, but potentially decreasing adaptive potential by decreasing genetic variability. We examined the ability of six genetically distinct and different-sized populations of a cold-water fish (brook trout, Salvelinus fontinalis) to tolerate acute thermal warming and whether this tolerance could be altered by hybridizing populations. Critical thermal maximum (CT max) assays were conducted on juveniles from each population to assess thermal tolerance, and the agitation temperature was recorded for assessing behavioural changes to elevated temperatures. An additional metric, which we have called the 'CT max-agitation window' (CT max minus agitation temperature), was also assessed. The CT max differed between five out of 15 population pairs, although the maximal CT max difference was only 0.68°C (29.11-29.79°C). Hybridization between one large population and two small populations yielded no obvious heterosis in mean CT max , and no differences in agitation temperature or CT max-agitation window were detected among pure populations or hybrids. Summer variation in temperature within each stream was negatively correlated with mean CT max and mean CT max-agitation window, although the maximal difference was small. Despite being one of the most phenotypically divergent and plastic north temperate freshwater fishes, our results suggest that limited variability exists in CT max among populations of brook trout, regardless of their population size, standing genetic variation and differing natural thermal regimes (temperature variation, minimum and maximum). This study highlights the level to which thermal tolerance is conserved between isolated populations of a vertebrate species, in the face of climate warming.

Scientific Data, Apr 3, 2019

Conservation Genetics

Conservation Physiology, 2016