CCMAR, CIMAR, Universidade do Algarve, Gambelas, Faro, Portugal.
BMC Ecol. 2010 Jul 12;10:17. doi: 10.1186/1472-6785-10-17.
Environmental heterogeneity plays a major role in invasion and coexistence dynamics. Habitat segregation between introduced species and their native competitors is usually described in terms of different physiological and behavioural abilities. However little attention has been paid to the effects of behaviour in habitat partitioning among invertebrates, partially because their behavioural repertoires, especially marine benthic taxa, are extremely limited. This study investigates the effect of gaping behaviour on habitat segregation of the two dominant mussel species living in South Africa, the invasive Mytilus galloprovincialis and the indigenous Perna perna. These two species show partial habitat segregation on the south coast of South Africa, the lower and upper areas of the mussel zone are dominated by P. perna and M. galloprovincialis respectively, with overlap in the middle zone. During emergence, intertidal mussels will either keep the valves closed, minimizing water loss and undergoing anaerobic metabolism, or will periodically open the valves maintaining a more efficient aerobic metabolism but increasing the risk of desiccation.
Our results show that, when air exposed, the two species adopt clearly different behaviours. M. galloprovincialis keeps the shell valves closed, while P. perna periodically gapes. Gaping behaviour increased water loss in the indigenous species, and consequently the risk of desiccation. The indigenous species expressed significantly higher levels of stress protein (Hsp70) than M. galloprovincialis under field conditions and suffered significantly higher mortality rates when exposed to air in the laboratory. In general, no intra-specific differences were observed in relation to intertidal height. The absence of gaping minimises water loss but exposes the invasive species to other stresses, probably related to anoxic respiration.
Gaping affects tolerance to desiccation, thus influencing the vertical zonation of the two species. Valve closure exposes the invasive species to higher stress and associated energy demands, but it minimizes water loss, allowing this species to dominate the upper mussel zone, where the gaping indigenous P. perna cannot survive. Thus even very simple behaviour can influence the outcome of interactions between indigenous and invasive species.
环境异质性在入侵和共存动态中起着重要作用。引入物种与其本地竞争者之间的栖息地隔离通常是根据不同的生理和行为能力来描述的。然而，人们很少关注行为对无脊椎动物栖息地划分的影响，部分原因是它们的行为范围，特别是海洋底栖生物，极其有限。本研究调查了张口行为对生活在南非的两种优势贻贝物种（入侵物种马氏珠母贝和本地物种厚壳贻贝）栖息地隔离的影响。这两个物种在南非南海岸显示出部分栖息地隔离，贻贝区的下部和上部区域分别由 P. perna 和 M. galloprovincialis 主导，中部区域存在重叠。在浮出水面期间，潮间带贻贝要么将壳瓣紧闭，最大限度地减少水分流失并进行无氧代谢，要么定期打开壳瓣，保持更高效的有氧代谢，但增加了干燥的风险。
我们的结果表明，当暴露在空气中时，这两个物种表现出明显不同的行为。M. galloprovincialis 保持壳瓣紧闭，而 P. perna 则定期张口。张口行为增加了本地物种的水分流失，从而增加了干燥的风险。在野外条件下，本地物种表达的应激蛋白（Hsp70）水平明显高于 M. galloprovincialis，而在实验室中暴露于空气中时，本地物种的死亡率明显更高。一般来说，在潮间带高度方面没有观察到种内差异。张口的缺失可最大限度地减少水分流失，但使入侵物种暴露于其他压力下，这些压力可能与缺氧呼吸有关。
张口行为影响对干燥的耐受性，从而影响两个物种的垂直分带。瓣紧闭使入侵物种面临更高的压力和相关的能量需求，但最大限度地减少水分流失，使该物种能够主导上部贻贝区，而张口的本地 P. perna 无法在那里生存。因此，即使是非常简单的行为也会影响本地和入侵物种之间相互作用的结果。
