As biodiversity declines toward the poles, high-latitude countries will contain the poleward range edge of many species, potentially focusing national conservation toward range-edge populations whose global conservation value remains contentious. Using the >200 vascular plants assessed for protection in Canada, we ask whether national species-conservation rankings are biased toward range-edge populations and supported by adequate research. Of 192 plant taxa deemed at-risk in Canada, 77% were only found in Canada at the northernmost 20% or less of their range. Higher threat categories had more peripheral taxa, and the mismatch between national and global threat rankings was greater for peripheral vs. non-peripheral taxa. Almost half (43%) of Canadian at-risk plants had not been studied in the peer-reviewed, conservation-relevant literature, 57% had not been studied in Canada, and peripheral populations received even less research effort than non-peripheral taxa. Only 5% of 7-9 conservation-relevant studies assessed at-risk populations in the context of their geographic range-information that is critical to establishing their relative conservation value. Thus, flora conservation in Canada is largely the conservation of edge populations, yet edge populations themselves and the geographic context that makes them unique are understudied, a research gap we must close to improve evidencebased conservation.
Populations that are asymmetrically isolated, such as above waterfalls, can sometimes export emigrants in a direction from which they do not receive immigrants, and thus provide an excellent opportunity to study the evolution of dispersal traits. We investigated the rheotaxis of guppies above barrier waterfalls in the Aripo and Turure rivers in Trinidad-the later having been introduced in 1957 from a below-waterfall population in another drainage. We predicted that, as a result of strong selection against downstream emigration, both of these above-waterfall populations should show strong positive rheotaxis. Matching these expectations, both populations expressed high levels of positive rheotaxis, possibly reflecting contemporary (rapid) evolution in the introduced Turure population. However, the two populations used different behaviors to achieve the same performance of strong positive rheotaxis, as has been predicted in the case of multiple potential evolutionary solutions to the same functional challenge (i.e., "many-to-one mapping"). By contrast, we did not find any difference in rheotactic behavior above versus below waterfalls on a small scale within either river, suggesting constraints on adaptive divergence on such scales.
15As biodiversity declines toward the poles, high-latitude countries will contain the poleward range 16 edge of many species, potentially focusing national conservation toward range-edge populations 17 whose global conservation value remains contentious. Using the >200 vascular plants assessed 18 for protection in Canada, we ask whether national species-conservation rankings are biased 19 toward range-edge populations and supported by adequate research. Of 192 plant taxa deemed 20 at-risk in Canada, 77% were only found in Canada at the northernmost 20% or less of their 21 range. Higher threat categories had more peripheral taxa, and the mismatch between national and 22 global threat rankings was greater for peripheral vs. non-peripheral taxa. Almost half (43%) of 23Canadian at-risk plants had not been studied in the peer-reviewed, conservation-relevant 24 literature, 57% had not been studied in Canada, and peripheral populations received even less 25 research effort than non-peripheral taxa. Only 5% of 7-9 conservation-relevant studies assessed 26 at-risk populations in the context of their geographic range-information that is critical to 27 establishing their relative conservation value. Thus, flora conservation in Canada is largely the 28 conservation of edge populations, yet edge populations themselves and the geographic context 29 that makes them unique are understudied, a research gap we must close to improve evidence-30 based conservation. 31 32 Keywords: species distributions, range limits, wildlife conservation, cold-edge populations, 33 endangered species, botanical diversity 34 35 2004; Glass et al. 2017) 48On one hand, peripheral populations may be less important to species' overall persistence 49 and harder to conserve than populations closer to the range core (Lesica and Allendorf 1995). In 50 the absence of dispersal barriers, range edges are thought to arise from declines in the abundance 51 and quality of habitat, such that peripheral populations are predicted to be less fit, smaller, and 52 more isolated than central populations (Brown et al. 1996;Eckert et al. 2008). Small populations 53 are more prone to genetic drift, which can lead to the fixation of deleterious mutations and 54 interfere with selection of favourable mutations, thereby eroding population fitness and adaptive 55 potential (Brown et al. 1996). This is particularly true of poleward populations that arose from 56 post-glacial range expansions, as expansion additionally reduces genetic diversity and fitness via 57 successive founder effects and 'surfing' of deleterious alleles (Waters et al. 2013; Pironon et al. 58
Invasive species have the potential to damage ecosystems outside their native range. At an invasion front, individuals are faced with the unfamiliar conditions of a novel environment. Therefore, certain behavioural traits such as boldness and movement likely play a role in invasion ecology. If behavioural traits of this kind are influenced by differing selection pressures between demographic groups of the same species, this could have broad implications for the management of expanding invasion fronts. To determine whether the invasive round goby (Neogobius melanostomus, Pallas, 1814) exhibits sex‐ and habitat‐based differences in boldness and movement across the invasion front, the authors assessed individual movement and exploration tendency under controlled lab settings using video analysis in a behavioural assay. N. melanostomus from lakes tended to be bolder than those from streams, and females tended to be bolder than males. This study provides evidence for sex‐ and habitat‐based differences in behaviour in this globally invasive species that the authors hope will assist in forming the foundation for contextually appropriate management strategies.
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