Isolation and characterization of 13 polymorphic microsatellite loci for the Florida pompano,Trachinotus carolinus

Here we describe 13 polymorphic, dinucleotide microsatellite loci for Trachinotus carolinus (Florida pompano), isolated by using PIMA, a polymerase chain reaction‐based technique. The number of alleles at each locus ranged from 3 to 29 (mean = 11.4) in 45 specimens collected from bay and nearshore waters around St Petersburg, Florida. Levels of expected and observed heterozygosities ranged from 0.15 to 0.94 (mean = 0.69) and from 0.16 to 0.98 (mean = 0.70), respectively. No significant departures from Hardy–Weinberg equilibrium expectations were observed. In exact tests for genotypic disequilibrium, there was no evidence of linkage for any pair of loci. The ability of these markers to cross‐amplify in two congeneric Trachinotus species —T. falcatus (permit) and T. goodei (palometa) — was also assessed. The loci were well‐resolved, highly polymorphic, and independently segregating in these taxa, also suggesting a general utility for intraspecific studies, species identification, and investigation of interspecific hybridization.     

Climate change and the decline of a once common bird

Climate change is predicted to negatively impact wildlife through a variety of mechanisms including retraction of range. We used data from the North American Breeding Bird Survey and regional and global climate indices to examine the effects of climate change on the breeding distribution of the Rusty Blackbird (Euphagus carolinus), a formerly common species that is rapidly declining. We found that the range of the Rusty Blackbird retracted northward by 143 km since the 1960s and that the probability of local extinction was highest at the southern range margin. Furthermore, we found that the mean breeding latitude of the Rusty Blackbird was significant and positively correlated with the Pacific Decadal Oscillation with a lag of six years. Because the annual distribution of the Rusty Blackbird is affected by annual weather patterns produced by the Pacific Decadal Oscillation, our results support the hypothesis that directional climate change over the past 40 years is contributing to the decline of the Rusty Blackbird. Our study is the first to implicate climate change, acting through range retraction, in a major decline of a formerly common bird species.     

Allometry and morphometrics of clypeal membrane size and shape in Nicrophorus (Coleoptera: Silphidae)

Contests between same‐sex opponents over resources necessary for reproduction, as well interactions used to discern mate quality, often involve exaggerated traits wherein large individuals have disproportionately larger traits. This positive allometric scaling of weapons or signals facilitates communication during social interactions by accentuating body size differences between individuals. Typically, males carry these exaggerated traits, as males must compete over limited female gametes. However, in Nicrophorus beetles both males and females engage in physical contests over the vertebrate carcasses they need to provision and raise offspring. Male and female Nicrophorus beetles have extended clypeal membranes directly above their mandibles, which could serve as signals. We investigated the scaling relationships between clypeal membrane size and shape and body size for five species of North American burying beetle to determine whether clypeal membranes contain exaggerated body size information. We found that clypeal membranes for both sexes of all species scaled positively with body size (slope > 1). Three of the five species also displayed sexual dimorphism in aspects of clypeal membrane size and shape allometry despite lack of dimorphism in body size. In two dimorphic species, small male clypeal membranes were statistically indistinguishable from the female form. We conclude that colored clypeal membranes in Nicrophorus beetles do contain exaggerated body size information. Observed patterns of dimorphism suggest that males sometimes experience stronger selection on marking size and shape, which might be explained by life history differences among species.