Low Mitochondrial DNA Variation in Double-crested Cormorants in Eastern North America

Double-crested Cormorant (Phohoiornx audus) numbers are increasing throughout eastern North America. We compared variation for five portions of mtDNA to determine if genetic differences existed among portions of the breeding range that would need to be considered when formulating management programs. Sequences for four mtDNA regions were identical across sample locations: frequencies of two haplotpes of the mitochondria1 Control Region were similar across sampling locations. There is no evidence of restricted gene flow among breeding areas, or between subspecies with different migratory patterns

Microsatellite Variation of Double-Crested Cormorant Populations in Eastern North America

Double-crested cormorants (Phalacrocorax auritus) exhibit highly adaptive and opportunistic foraging behavior. This flexibility in foraging and increases in population size have led to conflicts with aquaculture and recreational and commercial fishing (Duffy 1995). Although double-crested cormorants roosting in the lower Mississippi Valley appear to have minimal negative impact on sport fisheries, they may have a significant impact on commercial aquaculture production in this region (Glahn and Brugger 1995, Glahn et al. 1998). In 2003, the U.S. Fish and Wildlife Service released the Final Environmental Impact Statement on double-crested cormorant management allowing more flexibility in control of these birds in areas where they are negatively impacting aquaculture, habitat for nesting colonial waterbirds, and other public resources (U.S. Fish and Wildlife Service 2003). The U.S. Fish and Wildlife Service’s Final Rule expands the 1998 Public Resource Depredation Order (50 CFR 21.47) to permit control of double-crested cormorants at winter roost sites in the vicinity of aquaculture facilities

Data from: How far is too close? Restricted, sex-biased dispersal in black-capped vireos

Understanding the interplay of dispersal and how it translates into gene flow is key to understanding population processes, and especially so for endangered species occupying fragmented habitats. In migratory songbirds, there is evidence that long-distance movement capabilities are not highly related to observed dispersal. Our objectives were to 1) define the fine-scale spatial genetic structure in the endangered black-capped vireos to shed light on dispersal patterns, and 2) to relate dispersal dynamics to overall population genetic structure using a simulation approach. We sampled 160 individuals over two years to describe the fine-scale genetic structuring, and used this information to model scenarios to compare with actual data on change in population structuring over a 100-year interval. We found that black-capped vireo exhibit male-philopatry, and restricted dispersal distances, relative to females. Our simulations support a sex-biased dispersal model. Additionally, we find that fragmentation related changes in rates of dispersal might be a likely cause for increasing levels of population structure over a 100-year period. We show that restricted dispersal can explain population structuring in this species, and that changes in dispersal rates due to fragmentation may be a continuing threat to genetic viability in this species

Impacts of human recreation on carnivores in protected areas

<div><p>Mammalian carnivores can be particularly sensitive to human disturbance, even within protected areas (PAs). Our objective was to understand how human disturbance affects carnivore communities in southern Arizona, USA by studying habitat occupancy based on data collected using non-invasive methods in three PAs with different levels of human disturbance. Carnivore occupancy varied based on human disturbance variables (i.e., roads, trails, etc.). Common carnivore species (coyotes, gray foxes, and bobcats) had high occupancy probability in highly disturbed sites, while all other carnivore species had a higher probability of occupancy in low disturbance protected areas. Additionally, overall carnivore diversity was higher in PAs with low human disturbance. Edges of PAs appeared to negatively impact occupancy of nearly all carnivore species. We also found the presence of roads and trails, and not necessarily how much they are used, had a significant negative impact on the occupancy of most carnivore species. Furthermore, the overall level of disturbance within a PA influenced how sensitive carnivores were to human disturbance variables. Carnivores were more sensitive in PAs with higher levels of disturbance and were relatively unaffected by disturbance variables in a PA with low base levels of disturbance. Increased visitation to PAs, expected with the region’s high level of population growth, is likely to cause shifts in the carnivore communities favoring species that are less sensitive to disturbance.</p></div

Occupancy (±SE) of a) common and rare carnivores and b) 11 individual carnivore species in 3 protected areas of southern Arizona, 2014–2015.

<p>Species abbreviations: Badg = badger, BlBr = black bear, Bob = bobcat, Coy = coyote, GrFx = gray fox, HoSk = hooded skunk, KiFx = kit fox, MoLi = mountain lion, Rt = ringtail, SpSk = spotted skunk, StSk = striped skunk.</p

Using Genealogical Mapping and Genetic Neighborhood Sizes to Quantify Dispersal Distances in the Neotropical Passerine, the Black-Capped Vireo.

Dispersal is a key demographic process, ultimately responsible for genetic connectivity among populations. Despite its importance, quantifying dispersal within and between populations has proven difficult for many taxa. Even in passerines, which are among the most intensely studied, individual movement and its relation to gene flow remains poorly understood. In this study we used two parallel genetic approaches to quantify natal dispersal distances in a Neotropical migratory passerine, the black-capped vireo. First, we employed a strategy of sampling evenly across the landscape coupled with parentage assignment to map the genealogical relationships of individuals across the landscape, and estimate dispersal distances; next, we calculated Wright's neighborhood size to estimate gene dispersal distances. We found that a high percentage of captured individuals were assigned at short distances within the natal population, and males were assigned to the natal population more often than females, confirming sex-biased dispersal. Parentage-based dispersal estimates averaged 2400m, whereas gene dispersal estimates indicated dispersal distances ranging from 1600-4200 m. Our study was successful in quantifying natal dispersal distances, linking individual movement to gene dispersal distances, while also providing a detailed look into the dispersal biology of Neotropical passerines. The high-resolution information was obtained with much reduced effort (sampling only 20% of breeding population) compared to mark-resight approaches, demonstrating the potential applicability of parentage-based approaches for quantifying dispersal in other vagile passerine species