Data from: Climatic and geographic barriers drive distributional patterns of bird phenotypes within peninsular India

Modern phylogenetic data provide unparalleled ability to test
biogeographic paradigms, often suggested by differences in species
distribution patterns. However, such approaches have been applied less at
regional scales, particularly in Asia. In the absence of such data, we
examine if concordance of distributional patterns for phenotypes
(subspecies) suggest potential biogeographic barriers for birds in
peninsular India. Specifically, we examine climatic and physical factors
that might limit phenotype distributions in this region. Various physical,
vegetation and climatic barriers were demarcated to identify potential
biogeographic units within peninsular India. We then collated occurrence
of endemic or disjunctly distributed species and subspecies within these
units using published range maps. We also quantified turnover between
potential units, allowing us to identify significant biogeographic
barriers. Three time-step climate data (Last Glacial Maxima, mid-Holocene
and present) enabled us to examine differences between these potential
biogeographic regions through time. The Palk Straits, followed by the Goa
Gap (∼ 16°N) and the Godavari River emerged as the major barriers in this
region. The Palk Straits and Godavari are physical barriers while Goa Gap
appears to be a climate-mediated ecological divide. Mountain barriers like
the Palghat Gap are not the most significant barriers as previously
thought. Climatically intermediate regions appeared unstable in the past
and showed inconsistent affinities to different geographic units across
families. We suggest that relative climatic stability of the wet regions
of the southern western Ghats could be responsible for high subspecies
endemism here. Our approach provides hypotheses that can be tested with
comparative multi-species phylogeographic data in the future.

现代系统发育数据为检验生物地理学范式提供了前所未有的手段，此类范式往往由物种分布格局的差异所暗示。然而，此类研究方法在区域尺度上的应用相对匮乏，在亚洲地区尤为突出。鉴于此类数据的缺失，我们通过分析表型（亚种 (subspecies)）的分布格局一致性，探讨印度半岛区域内鸟类的潜在生物地理阻隔因素。具体而言，我们考察了可能限制该区域表型分布的气候与物理因子。我们划定了各类物理、植被与气候阻隔带，以识别印度半岛内部的潜在生物地理单元。随后，我们利用已发表的物种分布范围地图，整理了这些单元内特有或间断分布的物种与亚种的出现记录。我们还量化了潜在单元之间的物种更替率，借此识别出具有显著统计学意义的生物地理阻隔因素。我们借助三套时间尺度的气候数据（末次冰盛期 (Last Glacial Maxima)、中全新世及现代），得以探究这些潜在生物地理区域随时间推移的分异特征。帕尔科海峡 (Palk Straits)、果阿隘口 (Goa Gap，约16°N) 与戈达瓦里河 (Godavari River) 依次成为该区域的主要阻隔因素。其中，帕尔科海峡与戈达瓦里河属于物理阻隔，而果阿隘口则是由气候介导的生态分界带。诸如帕尔加特隘口 (Palghat Gap) 这类山地阻隔，并非如既往研究所认为的那样属于最关键的阻隔因素。气候过渡区域在过去似乎并不稳定，且在不同鸟类类群中，其与不同地理单元的分布亲和性均表现出不一致性。我们认为，南西部西高止山脉 (Western Ghats) 湿润区域相对稳定的气候条件，或许是该区域亚种特有性较高的核心原因。本研究提出的假说可在未来通过多物种种群比较系统发育数据开展验证。