Vegetation Correlates of the History and Density of Nesting by Ross’s Geese and Lesser Snow Geese at Karrak Lake, Nunavut

Growth in populations of Ross’s geese (Chen rossii) and lesser snow geese (C. caerulescens) has led to concerns about destructive grazing of Arctic ecosystems. We estimated the extent and composition of plant communities at Karrak Lake, Nunavut, where populations of both goose species have grown geometrically over the past three decades. Proportion of land covered by vegetation was lower in areas where geese had nested for more than 20 years than in areas with no previous nesting history. Vegetative cover also declined with increasing nest density of both species. Species richness and diversity of vegetation was higher in more recently colonized areas of nesting than in areas with over 20 years of goose nesting. Exposed mineral substrate, exposed peat, and Senecio congestus were more prevalent in areas with a 10-year or longer history of goose nesting than in areas with less than 10 years of nesting. These patterns confirm that increasing numbers of nesting Ross’s geese and lesser snow geese have altered the spatial distribution of vegetation surrounding Karrak Lake and reduced the species richness of local plant communities.La croissance des populations d’oie de Ross (Chen rossii) et de petite oie des neiges (C. caerulescens) engendre des préoccupations en matière de broutage destructif des écosystèmes de l’Arctique. Nous avons estimé l’ampleur et la composition des peuplements végétaux du lac Karrak, au Nunavut, où les populations de ces deux espèces d’oies ont augmenté de manière géométrique au cours des trois dernières décennies. La proportion de terre couverte par la végétation était moins élevée dans les régions où les oies avaient niché pendant plus de 20 ans que dans les régions où ces oies n’avaient jamais niché. Par ailleurs, la couverture végétale affichait une baisse là où la densité de nidification des deux espèces augmentait. La richesse des espèces et la diversité de la végétation étaient plus grandes dans les lieux de nidification colonisés plus récemment que dans les lieux de nidification colonisés il y a une vingtaine d’années. Les substrats de minéraux à découvert, la tourbe à découvert et le Senecio congestus se voyaient plus souvent dans les régions où les oies avaient niché pendant dix ans ou plus que dans les régions où les oies avaient niché pendant moins de dix ans. Ces tendances confirment que les populations croissantes d’oies de Ross et de petites oies des neiges ont altéré la répartition spatiale de la végétation entourant le lac Karrak, en plus de réduire la richesse des espèces et des peuplements végétaux des environs

Transcriptome profiling of chemosensory appendages in the malaria vector Anopheles gambiae reveals tissue- and sex-specific signatures of odor coding

<p>Abstract</p> <p>Background</p> <p>Chemosensory signal transduction guides the behavior of many insects, including <it>Anopheles gambiae</it>, the major vector for human malaria in sub-Saharan Africa. To better understand the molecular basis of mosquito chemosensation we have used whole transcriptome RNA sequencing (RNA-seq) to compare transcript expression profiles between the two major chemosensory tissues, the antennae and maxillary palps, of adult female and male <it>An. gambiae</it>.</p> <p>Results</p> <p>We compared chemosensory tissue transcriptomes to whole body transcriptomes of each sex to identify chemosensory enhanced genes. In the six data sets analyzed, we detected expression of nearly all known chemosensory genes and found them to be highly enriched in both olfactory tissues of males and females. While the maxillary palps of both sexes demonstrated strict chemosensory gene expression overlap, we observed acute differences in sensory specialization between male and female antennae. The relatively high expression levels of chemosensory genes in the female antennae reveal its role as an organ predominately assigned to chemosensation. Remarkably, the expression of these genes was highly conserved in the male antennae, but at much lower relative levels. Alternatively, consistent with a role in mating, the male antennae displayed significant enhancement of genes involved in audition, while the female enhancement of these genes was observed, but to a lesser degree.</p> <p>Conclusions</p> <p>These findings suggest that the chemoreceptive spectrum, as defined by gene expression profiles, is largely similar in female and male <it>An. gambiae</it>. However, assuming sensory receptor expression levels are correlated with sensitivity in each case, we posit that male and female antennae are perceptive to the same stimuli, but possess inverse receptive prioritizations and sensitivities. Here we have demonstrated the use of RNA-seq to characterize the sensory specializations of an important disease vector and grounded future studies investigating chemosensory processes.</p