Resource specialisation and the divergence of killer whale populations.
Resource specialisation and the divergence of killer whale populations.
复制标题
资源专业化和虎鲸种群的分化。
DOI：
10.1038/hdy.2015.45
复制
发表时间：
2015
期刊：
影响因子：
3.8
通讯作者：
Hoelzel AR
中科院分区：
文献类型：
--
作者：
Hoelzel AR
个体资源专门化在与竞争和生态机会相关的自然种群中很常见（见Aroujo等人，2011），并且以虎鲸（社会群体专门化）和其他海豚类鲸目动物而闻名（见Hoelzel， 2002）。猎物的选择影响捕食者对栖息地使用的时间和空间格局。对于虎鲸来说，社会群体（豆荚）了解猎物资源季节性丰富的地方，以及有效利用不同资源所需的技术。一些鱼类的猎物，特别是溯河产卵的物种，如鲑鱼，可能提供可预测的季节性丰富的浓度，而海洋哺乳动物的猎物可能更零散地分布，并显示出不同的时间丰度（和可及性）模式。然而，这些资源都是在同一水域内发现的，尽管捕获的时间和技术可能不同。Foote和Morin（2015）认为，同一海洋中种群的共存并不一定意味着它们在同属关系上存在差异，这显然是正确的。然而，正如Moura et al.（2015）和其他人（例如Hoelzel et al., 1998,2007）所讨论的那样，虎鲸的生活史和行为表明了同族分化的潜力。尽管资源的邻近性使虎鲸群进入了同族关系，但空间和时间使用的不同模式，以及对以相似的学习方法觅食的荚体的忠诚，可能会使资源专家群落在繁殖上隔离开来。可以想象，在过去的某个相关时期，北太平洋的海洋哺乳动物和鱼类猎物资源在地理上更加孤立，但没有数据表明情况确实如此。Foote和Morin（2015）提出，同属系统的分化是特殊的，仅限于“地理上孤立的”岛屿“种群，例如在小型火山口湖或偏远的小型海洋岛屿上发现的”。他们并不是唯一持这种观点的人，但其他的解释已经得到了很好的确立（参见Via（2001）的综述），事实上，一些最彻底调查的同域物种形成的假设例子并不符合Foote和Morin（2015）提出的情景，例如栖息地转移系统（例如，Filchak等人，2000）。尽管Foote和Morin（2015）认为虎鲸生态型分化太大，甚至不能代表“姐妹类群或单系特有物种群”，因此排除了同系物种形成的可能性，但我们指出，分化水平相对较低，并提出，如果物种形成与虎鲸有关，那也是在非常早期的阶段（见Moura等人，2014a, b）。然而，Moura et al.（2014a）利用限制性限制相关DNA （RAD）测序鉴定了3281个单核苷酸多态性（snp），将中性位点的分化与基于离群值分析和固定差异的定向选择推定的分化进行了比较，发现具有相关功能（与消化、生长等相关）的连锁位点的分化更强。这与生态类型之间的破坏性选择是一致的，被认为是同域物种形成过程中的一个重要机制（见Via， 2001）。Foote和Morin（2015）根据Foote等人（2011）的推断，提出线粒体DNA （mtDNA）系统发育所显示的人口历史反映了真实的历史，这意味着在异族中分化的资源专家群体的重新融合。然而，这是公认的（例如，见Shaw， 2002），单基因树可能会误导基于随机因素或渗入。随机效应特别可能出现在一棵树上，因为它很浅……
Individual resource specialisation is common in natural populations associated with competition and ecological opportunity (see Aroujo et al., 2011), and well known for the killer whale (where social groups specialise) and other delphinid cetaceans (see Hoelzel, 2002). Prey choice affects a predator’s temporal and spatial pattern of habitat use. For the killer whale, social groups (pods) learn where prey resources are seasonally abundant, and the techniques required to exploit different resources efficiently. Some fish prey, especially anadromous species such as salmon, may provide predictable seasonally rich concentrations, whereas marine mammal prey may be more patchily distributed and show a different pattern of temporal abundance (and accessibility). However, these resources are found within the same waters, though the timing and technique for capture may differ. Foote and Morin (2015) suggest that the co-occurrence of populations in the same ocean doesn't necessarily imply that they differentiated in sympatry, which is clearly true. However, as Moura et al.(2015) and others (for example, Hoelzel et al., 1998, 2007) have discussed, it is the life history and behaviour of killer whales that suggest the potential for differentiation in sympatry. Although the proximity of resources brings killer whale pods into sympatry, the differential pattern of spatial and temporal habitat use, as well as fidelity to pods that forage by similar learned methods, could serve to isolate resource specialist communities reproductively. It is conceivable that marine mammal and fish prey resources were more geographically isolated in the North Pacific during some relevant period in the past, but there are no data to indicate that this was the case. Foote and Morin (2015) propose that differentiation in sympatry is exceptional, restricted to ‘geographically isolated ‘island’populations, such as found in small crater lakes or on small remote oceanic islands’. They are not alone in this view, but alternative interpretations are well established (see review in Via (2001)), and indeed some of the most thoroughly investigated putative examples of sympatric speciation do not fit the scenarios proposed by Foote and Morin (2015), such as habitat-shift systems (for example, Filchak et al., 2000). Although Foote and Morin (2015) contend that killer whale ecotypes are too differentiated to represent even ‘sister taxa or a monophyletic endemic species flock’and therefore rule out speciation in sympatry, we point out that levels of differentiation are comparatively low, and propose that if speciation is relevant for killer whales it is at a very early stage (see Moura et al., 2014a, b). However, Moura et al.(2014a) using restriction-associated DNA (RAD) sequencing to identify 3281 single-nucleotide polymorphisms (SNPs) compared differentiation at neutral loci and those putatively under directional selection based on outlier analysis and fixed differences, and found stronger differentiation at linked loci with relevant functions (associated with digestion, growth etc.). This is consistent with disruptive selection between ecotypes, thought to be an important mechanism in the process of sympatric speciation (see Via, 2001). Foote and Morin (2015), following inference from Foote et al.(2011), propose that the demographic history indicated by mitochondrial DNA (mtDNA) phylogenies reflects the true history, and that it implies re-convergence of resource specialist populations that differentiated in allopatry. However, it is well-established (for example, see Shaw, 2002) that single gene trees can be misleading based on stochastic factors or introgression. Stochastic effects are especially likely for a tree that is as shallow for …