The role of sex in driving genetic variation and generating higher biodiversity has been debated for over a century. Speeding up evolution may increase genetic variation, but surprisingly it can reduce species diversity, according to a study led by Carlos J. Melian, "is that if sex increases genetic variation and speeds up evolution, then ecosystems will have a higher number of species that reproduce sexually. However, the connection between high reproductive speed and a higher number of species is a big jump, because little work has been done on the impact of sex on biodiversity. To explore the impact of sex on biodiversity, the researchers developed new theoretical models, based on ecological and evolutionary dynamics, to connect the mode of reproduction - whether sexual or asexual - to the origin of species and resulting biodiversity. They found that an increased genetic variation and the rate of generation of new species had little effect on general biodiversity.

Sexual reproduction is widely regarded as one of the major unexplained phenomena in biology. Nonetheless, while a general answer may remain elusive, considerable progress has been made in the last few decades. Here we fist review the genesis of, and support for, the major ecological hypotheses for biparental sexual reproduction.

Carassius gibelio is an extraordinary cyprinid species exhibiting both sexual and asexual reproduction. We hypothesized that parasitism selection is one of the potential mechanisms contributing to the coexistence of the two reproductive forms of C. We performed a four-year study to investigate the dynamics of parasite infection in C.