Data from: Climatic niche evolution is faster in sympatric than allopatric lineages of the butterfly genus Pyrgus

Understanding how speciation relates to ecological divergence has long
fascinated biologists. It is assumed that ecological divergence is
essential to sympatric speciation, as a mechanism to avoid competition and
eventually lead to reproductive isolation, while divergence in allopatry
is not necessarily associated with niche differentiation. The impact of
the spatial context of divergence on the evolutionary rates of abiotic
dimensions of the ecological niche has rarely been explored for an entire
clade. Here, we compare the magnitude of climatic niche shifts between
sympatric versus allopatric divergence of lineages in butterflies. By
combining next-generation sequencing, parametric biogeography and
ecological niche analyses applied to a genus-wide phylogeny of Palaearctic
Pyrgus butterflies, we compare evolutionary rates along eight climatic
dimensions across sister lineages that diverged in large-scale sympatry
versus allopatry. In order to examine the possible effects of the spatial
scale at which sympatry is defined, we considered three sets of
biogeographic assignments, ranging from narrow to broad definition. Our
findings suggest higher rates of niche evolution along all climatic
dimensions for sister lineages that diverge in sympatry, when using a
narrow delineation of biogeographic areas. This result contrasts with
significantly lower rates of climatic niche evolution found in cases of
allopatric speciation, despite the biogeographic regions defined here
being characterized by significantly different climates. Higher rates in
allopatry are retrieved when biogeographic areas are too widely defined—in
such a case allopatric events may be recorded as sympatric. Our results
reveal the macro-evolutionary significance of abiotic niche
differentiation involved in speciation processes within biogeographic
regions, and illustrate the importance of the spatial scale chosen to
define areas when applying parametric biogeographic analyses.

长期以来，生物学家一直致力于解析物种形成与生态分化之间的关联。学界普遍认为，生态分化是同域物种形成（sympatric speciation）的核心要件——其作为规避种间竞争、最终促成生殖隔离的机制，而异域物种形成（allopatric speciation）则未必与生态位分化（niche differentiation）相关联。针对整个演化支而言，分化的空间背景对生态位非生物维度演化速率的影响，迄今鲜有研究涉足。本研究针对蝴蝶类群，比较了同域分化与异域分化支系间的气候生态位位移（climatic niche shifts）幅度。我们结合下一代测序（next-generation sequencing）、参数化生物地理学（parametric biogeography）以及生态位分析方法，针对古北界Pyrgus属弄蝶的全属系统发育树开展研究，对比了在大范围同域环境下分化的姊妹支系与异域分化姊妹支系在8项气候维度上的演化速率。为探究同域性定义的空间尺度可能产生的影响，我们设置了三套生物地理区划方案，覆盖从窄到宽的定义范围。研究结果显示，当采用较窄的生物地理区域界定标准时，同域分化的姊妹支系在所有气候维度上的生态位演化速率均更高。这一结果与异域物种形成案例中观测到的显著更低的气候生态位演化速率形成鲜明对比——尽管本研究划定的生物地理区域本身气候差异显著。当生物地理区域界定过宽时，异域分化支系的生态位演化速率反而更高——此种情况下异域事件可能被误判为同域事件。本研究揭示了生物地理区域内物种形成过程中非生物生态位分化的宏观演化意义，并阐明了在开展参数化生物地理学分析时，空间尺度选择对区域界定的重要性。