Aim Our aim was to investigate genetic structure in Neotropical populations of common green iguanas (Iguana iguana) and to compare that structure with past geological events and present barriers. Additionally, we compared levels of divergence between lineages within Iguana with those within closely related genera in the subfamily Iguaninae. Location Neotropics. Methods DNA sequence data were collected at four loci for up to 81 individuals from 35 localities in 21 countries. The four loci, one mitochondrial (ND4) and three nuclear (PAC, NT3, c‐mos), were chosen for their differences in coalescent and mutation rates. Each locus was analysed separately to generate gene trees, and in combination in a species‐level analysis. Results The pairwise divergence between Iguana delicatissima and I. iguana was much greater than that between sister species of Conolophus and Cyclura and non‐sister species of Sauromalus, at both mitochondrial (mean 10.5% vs. 1.5–4%, respectively) and nuclear loci (mean 1% vs. 0–0.18%, respectively). Furthermore, divergences within I. iguana were equal to or greater than those for interspecific comparisons within the outgroup genera. Phylogenetic analyses yielded four strongly supported, geographically defined mitochondrial clades (3.8–5% divergence) within I. iguana. Three of the four clades were found using PAC (0.18–1.65% divergence) and two using NT3 (0.6% divergence) alone. The primary divergence, recovered in three polymorphic loci, was between individuals north and south of the Isthmus of Panama. The southern group was differentiated into clades comprising individuals on either side of the northern Andes, using both PAC and ND4. Main conclusions Deep genetic divergences were found within I. iguana that are congruent with past and current geological barriers. These divisions are greater than sister species comparisons in other Iguaninae genera, indicating the possible presence of cryptic species. Geological changes from the mid‐Miocene through the Plio‐Pleistocene have shaped the pattern of divergence in I. iguana. The uplift of the northern Andes presented a barrier between South American I. iguana populations by 4 Ma. Populations north of the Isthmus of Panama form a clade that is distinct from those to the south, and may have expanded northwards following the closing of the Isthmus of Panama 2.5 Ma.
Genetic diversity within species provides the raw material for adaptation and evolution. Just as regions of high species diversity are conservation targets, identifying regions containing high genetic diversity and divergence within and among populations may be important to protect future evolutionary potential. When multiple co-distributed species show spatial overlap in high genetic diversity and divergence, these regions can be considered evolutionary hotspots. We mapped spatial population genetic structure for 17 animal species across the Mojave Desert, USA. We analyzed these in concurrence and located 10 regions of high genetic diversity, divergence or both among species. These were mainly concentrated along the western and southern boundaries where ecotones between mountain, grassland and desert habitat are prevalent, and along the Colorado River. We evaluated the extent to which these hotspots overlapped protected lands and utility-scale renewable energy development projects of the Bureau of Land Management. While 30–40% of the total hotspot area was categorized as protected, between 3–7% overlapped with proposed renewable energy project footprints, and up to 17% overlapped with project footprints combined with transmission corridors. Overlap of evolutionary hotspots with renewable energy development mainly occurred in 6 of the 10 identified hotspots. Resulting GIS-based maps can be incorporated into ongoing landscape planning efforts and highlight specific regions where further investigation of impacts to population persistence and genetic connectivity may be warranted
In 1969, 17 pronghorn were reintroduced onto Umatilla Army Base in Oregon with no subsequent translocations or immigration into this fully enclosed area. We explored the genetic signature this event left on the population using a combination of microsatellite genotypes and mitochondrial DNA (mtDNA) sequencing data of this population. We compared the present day Umatilla herd to its source population and to a southeastern Oregon population. We found the reintroduced population had sharply lower genetic diversity compared to its source despite its rapid increase in population size following the initial founding event. It is likely the observed loss of diversity and the significant differentiation observed between the Umatilla herd and its source was a function of the low number of founders and stochastic losses of diversity in subsequent generations. We observed significant haplotypic and genotypic differentiation between the reintroduced population and its source (G ST = 0.063, F ST = 0.078, p < 0.001) that was approximately 3.5 times that found between the source and the southeastern population (G ST = 0.018, F ST = 0.021, p < 0.001). Moreover, 2 rare alleles in the source population were found in high frequency in the translocated population. The founding effect, stochastic shifts in allele frequencies each generation, restricted gene flow, and variance in the segregation of alleles related to a polygamous mating system have contributed to the significant differentiation observed between the Umatilla herd and its source. The results of this study can be applied directly to the management of ongoing translocation activities within Oregon.
The endangered Shivwits milkvetch, Astragalus ampullarioides, is a perennial, herbaceous plant. This Utah endemic was federally listed as endangered in 2001 because of its high habitat specificity and low numbers of individuals and populations. All habitat currently occupied by A. ampullarioides was designated as critical by the U.S. Fish and Wildlife Service in 2006 as a result of conservation litigation. We used AFLP markers to assess genetic differentiation among the seven extant populations and quantified genetic diversity in each. Six different AFLP markers resulted in 217 unambiguous polymorphic loci. We used multiple methods to examine any changes in population genetic structure in this species over time. Results indicate that A. ampullarioides had much higher gene flow among populations in the past, but has since fragmented into regional genetic units. These regions further fragmented genetically, and extant populations have differentiated through genetic drift. Populations had low levels of gene flow, even between geographically close populations. Rapid urban development reduces gene flow among regions and encroaches on populations of A. ampullarioides and remaining patches of unoccupied habitat. The genetic makeup of each of the extant populations should be carefully considered in management decisions such as population establishment or augmentation.
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