Department of Zoology, University of Otago, P.O. Box 56, Dunedin, 9054, New Zealand,
Parasitol Res. 2014 Jul;113(7):2593-602. doi: 10.1007/s00436-014-3913-x. Epub 2014 Apr 26.
Similarly to the division of labour in social insects, castes of morphologically distinct individuals exist within colonies of some species of parasitic trematodes. These colonies occur in the first intermediate host of the trematode's complex life cycle and are composed of clonal individuals. Individuals of the reproductive caste have significantly larger bodies while non-reproductive individuals are small and appear to be specialised for defence against co-infecting trematode colonies. In parallel with colony organisation of social insects, demographic traits such as the proportion of the small, non-reproducing individuals relative to the large, reproducing individuals and colony size are expected to vary and adjust to local conditions. In the case of colonies from geographically and potentially genetically distinct populations, this variation is hypothesised to become fixed by evolutionary divergence, as reported in social insect studies. In this study, the adaptive demography theory was further tested by looking at caste ratio and colony organisation of Philophthalmus sp. (a parasitic trematode with a recently discovered division of labour) colonies from geographically distinct populations. Results indicate that the caste ratio from geographically distinct Philophthalmus sp. colonies differs; the proportion of small, defensive individuals is higher in colonies from the location where the risk of competition is highest. This is suggestive of local adaptation, as caste ratios do not change over time under standardised laboratory conditions. This is the first evidence to support the adaptive demography theory in a species with a division of labour other than social insects.
与社会性昆虫的分工类似，某些寄生吸虫物种的群体中存在形态明显不同的虫型。这些群体出现在吸虫复杂生活史的第一中间宿主中，由克隆个体组成。生殖型个体的体型明显较大，而非生殖型个体则较小，似乎专门用于防御共生的吸虫群体感染。与社会性昆虫的群体组织平行，人口特征，如小的、非生殖个体与大的、生殖个体的比例以及群体大小，预计会发生变化并适应当地条件。在来自地理位置和潜在遗传上不同的群体的群体中，这种变化被假设通过进化分歧而固定下来，这在社会性昆虫研究中已有报道。在这项研究中，通过观察来自地理上不同的 Philophthalmus sp.（一种具有最近发现的分工的寄生吸虫）群体的虫型比例和群体组织，进一步测试了适应性人口统计学理论。结果表明，来自地理上不同的 Philophthalmus sp.群体的虫型比例存在差异；在竞争风险最高的地点的群体中，小型防御个体的比例较高。这表明存在局部适应性，因为在标准化实验室条件下，虫型比例不会随时间变化。这是支持具有不同于社会性昆虫的分工的物种中的适应性人口统计学理论的第一个证据。
