Data from: No evidence for maintenance of a sympatric Heliconius species barrier by chromosomal inversions

Mechanisms that suppress recombination are known to help maintain species barriers by preventing the breakup of co-adapted gene combinations. The sympatric butterfly species H. melpomene and H. cydno are separated by many strong barriers, but the species still hybridise infrequently in the wild, and around 40% of the genome is influenced by introgression. We tested the hypothesis that genetic barriers between the species are maintained by inversions or other mechanisms that reduce between-species recombination rate. We constructed fine-scale recombination maps for Panamanian populations of both species and their hybrids to directly measure recombination rate within and between species, and generated long sequence reads to detect inversions. We find no evidence for a systematic reduction in recombination rates in F1 hybrids, and also no evidence for inversions longer than 50 kb that might be involved in generating or maintaining species barriers. This suggests that mechanisms leading to global or local reduction in recombination do not play a significant role in the maintenance of species barriers between H. melpomene and H. cydno.

已知重组（recombination）抑制机制可通过阻止共适应基因组合的解体，助力维持物种屏障。同域分布的蝴蝶物种H. melpomene与H. cydno存在诸多强生殖隔离，但二者在野外仍会偶尔发生杂交，且约40%的基因组受到基因渐渗（introgression）的影响。我们验证了如下假说：物种间的遗传屏障由倒位（inversions）或其他可降低种间重组率的机制所维持。我们为两个物种及其杂交个体的巴拿马种群构建了高精度重组图谱，以直接测定种内与种间的重组率，并通过长读长测序序列（long sequence reads）检测倒位变异。研究发现，F1杂交一代的重组率并未出现系统性降低，也未发现长度超过50kb、可能参与形成或维持物种屏障的倒位变异。这表明，导致全局或局部重组率降低的机制，在维持H. melpomene与H. cydno之间的物种屏障方面并未发挥显著作用。