Skin morphology in cane toads

The structure of the skin may evolve rapidly during a biological invasion, for two reasons. First, novel abiotic challenges such as hydric conditions may modify selection on traits (such as skin thickness) that determine rates of evaporative water loss. Second, invaders might benefit from enhanced rates of dispersal, with locomotion possibly facilitated by thinner (and hence more flexible) skin. We quantified thickness of layers of the skin in cane toads (Rhinella marina) from the native range (Brazil), a stepping-stone population (Hawai’i), and the invaded range in Australia. Overall, the skin is thinner in cane toads in Australia than in the native range, consistent with selection on mobility. However, layers that regulate water exchange (epidermal stratum corneum and dermal Ground Substance layer) are thicker in Australia, retarding water loss in hot dry conditions. Within Australia, epidermal thickness increased as the toads colonised more arid regions, but then decreased in the ari...生物入侵过程中，生物体的皮肤结构可能快速演化，原因有二。其一，诸如水分条件这类新型非生物胁迫（abiotic challenges），可能改变对决定蒸发失水速率的性状（如皮肤厚度）的选择压力；其二，入侵种群或可从扩散速率提升中获益，而更薄（因而更具柔韧性）的皮肤可能助力运动能力。 本研究对来自原生分布区（巴西）、位于夏威夷的踏脚石种群（stepping-stone population）以及澳大利亚入侵分布区的蔗蟾（cane toad, Rhinella marina）的皮肤各层厚度进行了量化分析。 总体而言，澳大利亚蔗蟾的整体皮肤厚度低于原生分布区种群，这与运动能力相关的选择压力相符。不过，调控水分交换的皮肤层——表皮角质层（epidermal stratum corneum）与真皮基质层（dermal Ground Substance layer）——在澳大利亚种群中更厚，可在炎热干燥的环境中延缓水分流失。 在澳大利亚境内，随着蔗蟾定居的区域愈发干旱，其表皮厚度逐渐增加，但在[原文此处未完整表述]