No abstract

The amount of dispersal that occurs among populations can be limited by landscape heterogeneity, which is often due to both natural processes and anthropogenic activity leading to habitat loss or fragmentation. Understanding how populations are structured and mapping existing dispersal corridors among populations is imperative to both determining contemporary forces mediating population connectivity, and informing proper management of species with fragmented populations. Furthermore, the contemporary processes mediating gene flow across heterogeneous landscapes on a large scale are understudied, particularly with respect to widespread species. This study focuses on a widespread game bird, the Ruffed Grouse (Bonasa umbellus), for which we analyzed samples from the western extent of the range. Using three types of genetic markers, we uncovered multiple factors acting in concert that are responsible for mediating contemporary population connectivity in this species. Multiple genetically distinct groups were detected; microsatellite markers revealed six groups, and a mitochondrial marker revealed four. Many populations of Ruffed Grouse are genetically isolated, likely by macrogeographic barriers. Furthermore, the addition of landscape genetic methods not only corroborated genetic structure results, but also uncovered compelling evidence that dispersal resistance created by areas of unsuitable habitat is the most important factor mediating population connectivity among the sampled populations. This research has important implications for both our study species and other inhabitants of the early successional forest habitat preferred by Ruffed Grouse. Moreover, it adds to a growing body of evidence that isolation by resistance is more prevalent in shaping population structure of widespread species than previously thought.

Citation: Schamp, B. S., and A. M. Jensen. 2019. Evidence of limiting similarity revealed using a conservative assessment of coexistence.Abstract. The concept of limiting similarity is important in ecology because it encapsulates the expectation under niche theory that differences among species are fundamental to coexistence. A growing body of research has tested for evidence of limiting similarity, but only a small number of studies have produced support. Here, using relevant field data, we highlight one possible explanation for the paucity of support for limiting similarity. We test whether coexisting plant species that share bees as pollinators flower asynchronously, a form of temporal niche separation consistent with limiting similarity. Our results provide evidence of limiting similarity, adding to the small collection of null modeling studies that have thus far done so. Our work also provides evidence that temporal niche variation may be an important niche axis that broadly contributes to species coexistence. Finally, we demonstrate that a more conservative assessment of coexistence that includes only individual plants that have achieved reproduction, is consequential in whether we find evidence of significant flowering asynchrony in this study. We conclude that the conservative approach to assessing coexistence that we present here can reduce noise in coexistence data, improving our power to test for evidence consistent with limiting similarity. Using this approach may or may not result in an increase in evidence supporting limiting similarity; however, it will certainly give researchers more confidence that they have not missed existing evidence of limiting similarity.

Courtship displays are typically comprised of the same behavioral pattern, or patterns, repeated several times by males. Both the quantity and quality of the displays produced by a given male bird are not, however, constant. The number and/or quality of displays can decrease over time, indicating fatigue, or males can increase the number and/or quality as they display more, indicating a warm‐up period. Although there is evidence for fatigue or warm‐up periods for many types of courtship displays, data on motor components of avian courtship are scant, despite how commonly they are used. Here, we test whether drumming, a non‐vocal motor display, in male ruffed grouse (Bonasa umbellus) changes in relation to the number of displays executed. Using a large number of recordings, our linear mixed models yielded a significant effect of cumulative number of drumming displays on the number of wingbeats per second, referred to as pulse rate. Across males, pulse rate is slowest when males begin drumming each day and increases until approximately 50 drumming displays have been produced. The rate of increase is also modulated by the nighttime low temperature such that cooler conditions are associated with lower pulse rates and a slower increase in pulse rate relative to the cumulative number of displays. Further, the maximum pulse rate recorded and average pulse rate after 50 displays is inversely correlated with body mass such that larger males are slower than smaller males. We suggest that the daily changes in pulse rate likely reflect a warm‐up period based upon the effects of cumulative drumming count and temperature on pulse rate. Whether these dynamic changes in the production of a motor display are informative to female grouse is unknown. However, we propose that daily changes in how motor displays are performed may be a common feature of avian courtship that has gone relatively unnoticed, despite the potential for motor performance to be a trait that is important for female mate choice.

The expansion of invasive non-indigenous species in the Mediterranean is generating an increasing concern about biodiversity protection and human health, with European countries being solicited to apply early warning measures in such circumstances. The recent expansion of the hazardous fish Lagocephalus sceleratus in the Straits of Sicily, the subsequent actions adopted to manage the risk and the feedback received from the public are herein presented, as an example of the interaction between experts and the public in promoting scientific citizenship through an ad hoc action. A rapid increase in media reports related to L. sceleratus had been registered after the launch of the early warning campaign as part of a scientific and health risk communication strategy, and seven new records of this species have emerged shortly after. This study represents a useful contribution to the further bridging of the science-policy gap.