Evolutionary models demonstrate rapid and adaptive diversification of Australo-Papuan pythons

Lineages may diversify when they encounter available ecological niches.
Adaptive divergence by ecological opportunity often appears to follow the
invasion of a new environment with open ecological space. This
evolutionary process is hypothesized to explain the explosive
diversification of numerous Australian vertebrate groups following the
collision of the Eurasian and Australian plates 25 million years ago. One
of these groups is the pythons, which demonstrate their greatest
phenotypic and ecological diversity in Australo-Papua (Australia and New
Guinea). Here, using an updated and near complete time-calibrated
phylogenomic hypothesis of the group, we show that following invasion of
this region, pythons experienced a sudden burst of speciation rates
coupled with multiple instances of accelerated phenotypic evolution in
head and body shape and body size. These results are consistent with
adaptive radiation theory with an initial rapid niche filling phase and
later slow-down approaching niche saturation. We discuss these findings in
the context of other Australo-Papuan adaptive radiations and the
importance of incorporating adaptive diversification systems that are not
extraordinarily species-rich but ecomorphologically diverse to understand
how biodiversity is generated.

演化支（lineages）在遭遇可利用的生态位（ecological niches）时可能发生分化。由生态机遇（ecological opportunity）驱动的适应性分化（adaptive divergence），往往出现在入侵拥有开放生态空间的新环境之后。学界假说该演化过程可解释2500万年前欧亚板块与澳大利亚板块碰撞后，众多澳大利亚脊椎动物类群的爆发式演化分化。其中一类类群便是蟒科（pythons）动物，它们在澳大拉西亚-巴布亚地区（Australo-Papua，即澳大利亚与新几内亚）展现出最为显著的表型与生态多样性。本研究依托该类群经更新且近乎完整的时间校准系统发育组学假说（time-calibrated phylogenomic hypothesis），揭示在入侵该区域后，蟒科动物经历了物种形成速率（speciation rates）的突增，同时伴随头部、躯体形态以及体型的多起加速表型演化（phenotypic evolution）事件。上述结果与适应性辐射（adaptive radiation）理论相符：初始阶段为快速的生态位填充过程，后续则逐渐放缓直至接近生态位饱和（niche saturation）状态。我们将结合其他澳大拉西亚-巴布亚地区的适应性辐射案例讨论本研究发现，并探讨纳入那些并非物种数量极多、但生态形态多样的适应性分化系统，对于理解生物多样性产生机制的重要意义。