Bierbach David, Arias-Rodriguez Lenin, Plath Martin
Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), 86150 Villahermosa, Tabasco, México.
Curr Zool. 2018 Feb;64(1):125-133. doi: 10.1093/cz/zox071. Epub 2017 Nov 28.
During adaptation to different habitat types, both morphological and behavioral traits can undergo divergent selection. Males often fight for status in dominance hierarchies and rank positions predict reproductive success. Ecotypes with reduced fighting abilities should have low reproductive success when migrating into habitats that harbor ecotypes with superior fighting abilities. Livebearing fishes in the -species complex inhabit not only regular freshwater environments, but also independently colonized sulfidic (HS-containing) habitats in three river drainages. In the current study, we found fighting intensities in staged contests to be considerably lower in some but not all sulfidic surface ecotypes and the sulfidic cave ecotype compared with populations from non-sulfidic surface sites. This is perhaps due to selection imposed by HS, which hampers oxygen uptake and transport, as well as cellular respiration. Furthermore, migrants from sulfidic habitats may lose fights even if they do not show overall reduced aggressiveness, as physiological performance is likely to be challenged in the non-sulfidic environment to which they are not adapted. To test this hypothesis, we simulated migration of HS-adapted males into HS-free waters, as well as HS-adapted cave-dwelling males into sulfidic surface waters. We found that intruders established dominance less often than resident males, independent of whether or not they showed reduced aggressiveness overall. Our study shows that divergent evolution of male aggressive behavior may also contribute to the maintenance of genetic differentiation in this system and we call for more careful evaluation of male fighting abilities in studies on ecological speciation.
在适应不同栖息地类型的过程中，形态和行为特征都可能经历趋异选择。雄性常常在优势等级制度中争夺地位，等级位置预示着繁殖成功率。战斗能力降低的生态型在迁入具有更强战斗能力生态型的栖息地时，繁殖成功率应该较低。某物种复合体中的卵胎生鱼类不仅栖息于常规淡水环境，还在三条河流流域独立定殖于含硫（含HS）的栖息地。在本研究中，我们发现，与来自非含硫地表水栖息地的种群相比，在某些（但并非所有）含硫地表水生态型和含硫洞穴生态型中， staged contests中的战斗强度要低得多。这可能是由于HS施加的选择，它会阻碍氧气摄取和运输以及细胞呼吸。此外，来自含硫栖息地的迁入者即使没有表现出整体攻击性降低，也可能输掉战斗，因为它们的生理表现可能会在它们未适应的非含硫环境中受到挑战。为了验证这一假设，我们模拟了适应HS的雄性迁入无HS水域，以及适应HS的洞穴雄性迁入含硫地表水水域的情况。我们发现，入侵者建立优势地位的频率低于常驻雄性，无论它们是否整体表现出攻击性降低。我们的研究表明，雄性攻击行为的趋异进化也可能有助于维持该系统中的遗传分化，我们呼吁在生态物种形成研究中更仔细地评估雄性战斗能力。
