Showing papers by "Allan J. Baker published in 2009"
TL;DR: An adaptive management strategy with recovery goals and annual monitoring is proposed that will both allow red knot and horseshoe crab populations to recover and permit a sustainable harvest of horseshOE crabs.
Abstract: Each May, red knots (Calidris canutus rufa) congregate in Delaware Bay during their northward migration to feed on horseshoe crab eggs (Limulus polyphemus) and refuel for breeding in the Arctic. During the 1990s, the Delaware Bay harvest of horseshoe crabs for bait increased 10-fold, leading to a more than 90% decline in the availability of their eggs for knots. The proportion of knots achieving weights of more than 180 grams by 26–28 May, their main departure period, dropped from 0.6–0.8 to 0.14–0.4 over 1997–2007. During the same period, the red knot population stopping in Delaware Bay declined by more than 75%, in part because the annual survival rate of adult knots wintering in Tierra del Fuego declined. Despite restrictions, the 2007 horseshoe crab harvest was still greater than the 1990 harvest, and no recovery of knots was detectable. We propose an adaptive management strategy with recovery goals and annual monitoring that, if adopted, will both allow red knot and horseshoe crab populations to reco...
92 citations
TL;DR: This work addresses criticisms of a single mtDNA gene barcodes in birds because most species are known and thus provide an ideal test data set, and argues with selected examples that with the exception of thresholds these criticisms are not problematic for avian taxonomy.
Abstract: General criticisms of a single mtDNA gene barcodes include failure to identify newly evolved species, use of species-delimitation thresholds, effects of selective sweeps and chance occurrence of reciprocal monophyly within species, inability to deal with hybridization and incomplete lineage sorting, and superiority of multiple genes in species identification. We address these criticisms in birds because most species are known and thus provide an ideal test data set, and we argue with selected examples that with the exception of thresholds these criticisms are not problematic for avian taxonomy. Even closely related sister species of birds have distinctive COI barcodes, but it is not possible to universally apply distance thresholds based on ratios of within-species and among-species variation. Instead, more rigorous methods of species delimitation should be favoured using coalescent-based techniques that include tests of chance reciprocal monophyly, and times of lineage separation and sequence divergence. Incomplete lineage sorting is also easily detected with DNA barcodes, and usually at a younger time frame than a more slowly evolving nuclear gene. Where DNA barcodes detect divergent reciprocally monophyletic lineages, the COI sequences can be combined with multiple nuclear genes to distinguish between speciation or population subdivision arising from high female philopatry or regional selective sweeps. Although selective sweeps are increasingly invoked to explain patterns of shallow within-species coalescences in COI gene trees, caution is warranted in this conjecture because of limited sampling of individuals and the reduced power to detect additional mtDNA haplotypes with one gene.
72 citations
TL;DR: The passage population in 2004 of 18,000 Red Knot was substantially smaller than the recent peak count of 50,360 in 1998, which confirms a significant decline in the number of Red Knot staging in Delaware Bay.
Abstract: .— Many migratory birds use staging sites to gain essential resources to fuel their ongoing migration. Understanding staging strategies reveals much about migration systems and is essential if one is concerned with monitoring population trends and mass gains, two of the principal methods for assessing the “health” of a migratory population. In spring 2004, we investigated the staging behavior in Delaware Bay of Red Knot (Calidris canutus) using mark-recapture techniques and resightings of birds marked in the preceding spring. Individuals staged for 11–12 days, which declined to 8–10 days late in the season. Arrivals were asynchronous, but departures tended to be synchronized. A simple sensitivity analysis showed that the mark-recapture analysis estimated length of stay to within +10% and confirmed biases in monitoring trends and mass gains using peak counts and mass-on-date regressions. Alternative methods using staging duration to estimate passage population size and mass gains were shown to be u...
44 citations
TL;DR: Analyses of population genetic structure based on mtDNA showed evidence of two major populations in western and eastern Brazil that share a few lowfrequency haplotypes, and male-biased dispersal and female philopatry best explain the different patterns observed in these two markers.
Abstract: . Comparing the patterns of population differentiation among genetic markers with different modes of inheritance can provide insights into patterns of sex-biased dispersal and gene flow. The Blue-and-yellow Macaw (Ara ararauna) is a Neotropical parrot with a broad geographic distribution in South America. However, little is known about the natural history and current status of remaining wild populations, including levels of genetic variability. The progressive decline and possible fragmentation of populations may endanger this species in the near future. We analyzed mitochondrial DNA (mtDNA) control-region sequences and six microsatellite loci of Blue-and-yellow Macaws sampled throughout their geographic range in Brazil to describe population genetic structure, to make inferences about historical demography and dispersal behavior, and to provide insight for conservation efforts. Analyses of population genetic structure based on mtDNA showed evidence of two major populations in western and eastern ...
34 citations
TL;DR: The crested terns are a group of six species of seabirds with a world-wide distribution closely allied to but larger than typical Sterna species and form a strongly supported monophyletic clade.
32 citations
TL;DR: The authors isolated and tested 16 microsatellite loci in black‐tailed godwits from the Netherlands and from Australasia and found that all loci were autosomal and no significant linkage disequilibrium between the loci was observed.
Abstract: We isolated and tested 16 microsatellite loci in black-tailed godwits from the Netherlands (Limosa limosa limosa), and from Australasia (subspecies melanuroides). One locus was monomorphic, two loci had null-alleles and one was significantly heterozygote deficient. The remaining 12 polymorphic loci had on average 7.9 alleles (range 5-11) and the mean expected heterozygosity was 0.69. No significant linkage disequilibrium between the loci was observed and all loci were autosomal. Fourteen loci were successfully cross-amplified in bar-tailed godwit (Limosa lapponica).
7 citations
01 Jan 2009
TL;DR: A new subspecies of Coenocorypha snipe from Campbell I is described and named in this paper, which was discovered on rat-free 19 ha Jacquemart I in 1997, and had probably been confined there as a breeding species for about 170 years.
Abstract: A new subspecies of Coenocorypha snipe from Campbell I is described and named. This bird was discovered on rat-free 19 ha Jacquemart I in 1997, and had probably been confined there as a breeding species for about 170 years. Norway rats (Rattus norvegicus ) were eradicated from 11,268 ha Campbell I in 2001, and snipe soon began to recolonise the main island from Jacquemart I 1 km offshore. Twelve adults and 5 chicks were caught on Campbell I in Jan 2006, and 1 nest was found. Genetic analysis of blood samples, and measurements and plumage descriptions from these birds revealed that they were best regarded as a subspecies of Coenocorypha aucklandica, a species here recognised as confined to the subantarctic Auckland, Antipodes and Campbell Is, and specifically distinct from the 2 other extant Coenocorypha snipes (Snares I snipe C. huegeli and Chatham I snipe C. pusilla).
5 citations
1 citations