Salviano Maurício Barbosa, Cursino Marina Suzuki, Zanetti Eveline Dos Santos, Abril Vanessa Veltrini, Duarte José Maurício Barbanti
Laboratório de Histologia e Embriologia, Universidade Federal do Piauí, Terezina-PI, Brazil.
Núcleo de Pesquisa e Conservação de Cervídeos, Universidade Estadual Paulista, Jaboticabal-SP, Brazil.
Biol Reprod. 2017 Jun 1;96(6):1279-1287. doi: 10.1093/biolre/iox041.
The red brocket (Mazama americana) is a South American deer with a wide geographical distribution that presents different chromosomal variants depending on their location. At least six different cytotypes belonging to two distinct evolutionary lineages have been described. This study aimed to verify the existence of postzygotic reproductive isolation between cytotypes of M. americana by comparative evaluation of pure and hybrid males. Seven 18-month-old bucks were submitted to seminal collection and evaluation and testicle histological evaluations. The pure males showed normal parameters for sperm quality and testicular histology. Hybrids from the same evolutionary lineage (≤3 chromosomes different from the progenitors) showed similar results to pure males, except for the reduced ratio of round spermatids to pachytene spermatocytes. Hybrids between cytotypes of different evolutionary lineages (≥10 chromosomes different from progenitors) presented azoospermia and evidence of testicular degeneration. Despite the striking morphological similarities, we can conclude that populations with more distinct karyotypes possess an effective reproductive barrier; moreover, there is evidence that reproductive isolation mechanisms exist between some closer karyotypes, corroborating the hypothesis that M. americana is best characterized as a superspecies. Thus, the future description of several new species for this taxon is expected, since the tendency is to establish efficient mechanisms of postzygotic reproductive isolation, preventing the introgression and fusion of genomes from different populations through chromosome variation.
红短角鹿（Mazama americana）是一种分布广泛的南美鹿，根据其所处位置呈现出不同的染色体变体。目前已描述了至少六种属于两个不同进化谱系的不同细胞型。本研究旨在通过对纯种和杂种雄性进行比较评估，验证美洲短角鹿细胞型之间合子后生殖隔离的存在。七只18个月大的雄鹿接受了精液采集与评估以及睾丸组织学评估。纯种雄性的精子质量和睾丸组织学参数正常。来自同一进化谱系的杂种（与亲本相比有≤3条染色体不同）除了圆形精子细胞与粗线期精母细胞的比例降低外，结果与纯种雄性相似。不同进化谱系细胞型之间的杂种（与亲本相比有≥10条染色体不同）出现无精子症和睾丸退化迹象。尽管形态上有惊人的相似性，但我们可以得出结论，具有更明显核型的种群拥有有效的生殖屏障；此外，有证据表明一些亲缘关系较近的核型之间存在生殖隔离机制，这证实了美洲短角鹿最好被描述为一个超种的假设。因此，预计该分类群未来会描述几个新物种，因为趋势是建立有效的合子后生殖隔离机制，通过染色体变异防止不同种群的基因组渗入和融合。
