Dainson Miri, Mark Melissa, Hossain Marouf, Yoo Barney, Holford Mande, McNeil Shannon E, Riehl Christina, Hauber Mark E
Department of Animal Biology, School of Integrative Biology, University of Illinois at Urbana-Champaign, Champaign, IL, 61801, USA.
Landscape Conservation Initiative, Northern Arizona University, Flagstaff, AZ, 86011, USA.
J Chem Ecol. 2018 Oct;44(10):940-946. doi: 10.1007/s10886-018-0986-5. Epub 2018 Jul 6.
Hosts of avian brood parasites often use visual cues to reject foreign eggs, and several lineages of brood parasites have evolved mimetic eggshell coloration and patterning to circumvent host recognition. What is the mechanism of parasitic egg color mimicry at the chemical level? Mimetic egg coloration by Common Cuckoos Cuculus canorus is achieved by depositing similar concentrations of colorful pigments into their shells as their hosts. The mechanism of parasitic egg color mimicry at the chemical level in other lineages of brood parasites remains unexplored. Here we report on the chemical basis of egg color mimicry in an evolutionarily independent, and poorly studied, host-parasite system: the Neotropical Striped Cuckoo Tapera naevia and one of its hosts, the Rufous-and-white Wren Thryophilus rufalbus. In most of South America, Striped Cuckoos lay white eggs that are identical to those of local host species. In Central America, however, Striped Cuckoos lay blue eggs that match those of the Rufous-and-white Wren, suggesting that blue egg color in these cuckoo populations is an adaptation to mimic host egg appearance. Here we confirm that Striped Cuckoo eggs are spectrally similar to those of their hosts and consistently contain the same major eggshell pigment, biliverdin. However, wren eggshells lacked protoporphyrin, which was present in the parasitic cuckoo eggshells. Furthermore, biliverdin concentrations were significantly lower in cuckoo eggshells than in host eggshells. Similarity of host-parasite eggshell appearance, therefore, need not always be paralleled by a quantitative chemical match to generate effective visual mimicry in birds.
鸟类巢寄生的宿主通常利用视觉线索来拒绝外来卵，而几个巢寄生谱系已经进化出模仿蛋壳颜色和图案的能力，以规避宿主的识别。在化学层面上，寄生卵颜色模仿的机制是什么？普通杜鹃（Cuculus canorus）的模仿卵颜色是通过在其蛋壳中沉积与宿主相似浓度的彩色色素来实现的。在其他巢寄生谱系中，寄生卵颜色在化学层面上的模仿机制仍未得到探索。在这里，我们报告了一个在进化上独立且研究较少的宿主 - 寄生虫系统中卵颜色模仿的化学基础：新热带条纹杜鹃（Tapera naevia）及其宿主之一棕腹鹪鹩（Thryophilus rufalbus）。在南美洲的大部分地区，条纹杜鹃产白色的卵，这些卵与当地宿主物种的卵相同。然而，在中美洲，条纹杜鹃产蓝色的卵，与棕腹鹪鹩的卵相匹配，这表明这些杜鹃种群中的蓝色卵颜色是一种适应，用于模仿宿主卵的外观。在这里，我们证实条纹杜鹃的卵在光谱上与它们的宿主相似，并且始终含有相同的主要蛋壳色素——胆绿素。然而，鹪鹩的蛋壳中缺乏原卟啉，而寄生杜鹃的蛋壳中存在原卟啉。此外，杜鹃蛋壳中的胆绿素浓度明显低于宿主蛋壳中的浓度。因此，宿主 - 寄生虫蛋壳外观的相似性并不一定总是伴随着定量的化学匹配，就能在鸟类中产生有效的视觉模仿。
