Reproductive isolation is a heuristic, not a measure: a commentary on Westram et al., 2022

Biomod2 modeling for predicting the potential ecological distribution of three Fritillaria species under climate change

The Fritillaria species ranked as a well-known traditional medicine in China and has become rare due to excessive harvesting. To find reasonable strategy for conservation and cultivation, identification of new ecological distribution of Fritillaria species together with prediction of those responses to climate change are necessary. In terms of current occurrence records and bioclimatic variables, the suitable habitats for Fritillaria delavayi, Fritillaria taipaiensis, and Fritillaria wabuensis were predicted. In comparison with Maxent and GARP, Biomod2 obtained the best AUC, KAPPA and TSS values of larger than 0.926 and was chosen to construct model. Temperature seasonality was indicated to put the greatest influence on Fritillaria taipaiensis and Fritillaria wabuensis, while isothermality was of most importance for Fritillaria delavayi. The current suitable areas for three Fritillaria species were distributed in south-west China, accounting for approximately 17.72%, 23.06% and 20.60% of China's total area, respectively. During 2021-2100 period, the suitable habitats of F. delavayi and F. wabuensis reached the maximum under SSP585 scenario, while that of F. taipaiensis reached the maximum under SSP126 scenario. The high niche overlap among three Fritillaria species showed correlation with the chemical composition (P ≤ 0.05), while no correlation was observed between niche overlap and DNA barcodes, indicating that spatial distribution had a major influence on chemical composition in the Fritillaria species. Finally, the acquisition of species-specific habitats would contribute to decrease in habitat competition, and future conservation and cultivation of Fritillaria species.

Irregularities in Meiotic Prophase I as Prerequisites for Reproductive Isolation in Experimental Hybrids Carrying Robertsonian Translocations

The basic causes of postzygotic isolation can be elucidated if gametogenesis is studied, which is a drastically different process in males and females. As a step toward clarifying this problem, we obtained an experimental inbred lineage of the eastern mole vole Ellobius tancrei, whose founder animals were animals with identical diploid numbers 2n = 50 but with different Robertsonian translocations (Rb), namely 2Rb4.12 and 2Rb9.13 in the female and 2Rb.2.18 and 2Rb5.9 in the male. Here, we analyzed strictly inbred hybrids (F1, fertile and F10, sterile) using immunocytochemical methods in order to study spermatocytes during the meiotic prophase I. Previously, the presence of trivalents was assumed to have no significant effect on spermatogenesis and fertility in hybrids, but we demonstrated that spermatogenesis might be disturbed due to the cumulative effects of the retarded synapses of Rb bivalents as well as trivalents and their associations with XX sex bivalents. Alterations in the number of gametes due to the described processes led to a decrease in reproductive capacity up to sterility and can be examined as a mechanism for reproductive isolation, thus starting speciation.