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Evolutionary trade-off in reproduction of Cambrian arthropods

2020; American Association for the Advancement of Science; Volume: 6; Issue: 18 Linguagem: Inglês

10.1126/sciadv.aaz3376

2375-2548

Qiang Ou, Jean Vannier, Xianfeng Yang, Ailin Chen, Huijuan Mai, Degan Shu, Jian Han, Dongjing Fu, Rong Wang, Georg Mayer,

Marine and coastal plant biology

Trade-offs play a crucial role in the evolution of life-history strategies of extant organisms by shaping traits such as growth pattern, reproductive investment, and lifespan. One important trade-off is between offspring number and energy (nutrition, parental care, etc.) allocated to individual offspring. Exceptional Cambrian fossils allowed us to trace the earliest evidence of trade-offs in arthropod reproduction. †Chuandianella ovata, from the early Cambrian Chengjiang biota of China, brooded numerous (≤100 per clutch), small (Ø, ~0.5 mm) eggs under carapace flaps. The closely related †Waptia fieldensis, from the middle Cambrian Burgess Shale of Canada, also brooded young, but carried fewer (≤ 26 per clutch), larger (Ø, ~2.0 mm) eggs. The notable differences in clutch/egg sizes between these two species suggest an evolutionary trade-off between quantity and quality of offspring. The shift toward fewer, larger eggs might be an adaptive response to marine ecosystem changes through the early-middle Cambrian. We hypothesize that reproductive trade-offs might have facilitated the evolutionary success of early arthropods.