Limits to host colonisation and speciation in a radiation of parasitic finches

Parasite lineages vary widely in species richness. In some clades, speciation is linked to the colonisation of new hosts. This is the case in the indigobirds and whydahs (Vidua), brood-parasitic finches whose nestlings mimic the phenotypes of their specific hosts. To understand the factors limiting host colonisation, and therefore speciation, we simulated the colonisation of a host using cross-fostering experiments in the field. Despite DNA barcoding suggesting that host species feed their chicks similar diets, nestling Vidua had low survival in their new host environment. Nestling Vidua did not alter their begging calls plastically to match those of the new hosts, and were fed less compared to both host chicks and to Vidua chicks in their natural host nests. This suggests that a key hurdle in colonising new hosts is obtaining the right amount rather than the right type of food from host parents. This highlights the importance of mimetic nestling phenotypes in soliciting feeding from fo...

寄生生物支系的物种丰富度差异显著。在部分演化支中，物种形成过程与新宿主的定殖存在密切关联。此类情况见于靛蓝维达雀与辉蓝维达雀（Vidua）——这类巢寄生雀类的雏鸟可模拟其特定宿主的表型特征。为明确限制宿主定殖（进而影响物种形成）的关键因素，本研究通过野外跨巢抚育实验模拟了宿主定殖过程。尽管DNA条形码（DNA barcoding）检测结果显示，不同宿主物种饲喂雏鸟的食物类型较为相似，但维达雀雏鸟在新宿主环境中的存活率仍偏低。维达雀雏鸟无法通过可塑性调整其乞食鸣声以匹配新宿主雏鸟的鸣唱特征，且相较于宿主自身雏鸟以及自然宿主巢中的维达雀雏鸟，其获得的投喂量更少。这表明，定殖新宿主过程中的核心障碍并非获取宿主亲鸟提供的食物类型，而是获取足量的食物。这凸显了模拟雏鸟表型在向宿主亲鸟乞食过程中的重要性，[原文未完整呈现]