Humphries David J, Nelson-Flower Martha J, Bell Matthew B V, Finch Fiona M, Ridley Amanda R
Department of Biological Sciences Macquarie University Sydney New South Wales Australia.
Pied Babbler Research Project University of Cape Town Rondebosch Western Cape South Africa.
Ecol Evol. 2021 Nov 19;11(23):17031-17042. doi: 10.1002/ece3.8342. eCollection 2021 Dec.
Many species maintain territories, but the degree of overlap between territories and the level of aggression displayed in territorial conflicts can vary widely, even within species. Greater territorial overlap may occur when neighboring territory holders are close relatives. Animals may also differentiate neighbors from strangers, with more familiar neighbors eliciting less-aggressive responses during territorial conflicts (the "dear enemy" effect). However, research is lacking in how both kinship and overlap affect territorial conflicts, especially in group-living species. Here, we investigate kinship, territorial overlap, and territorial conflict in a habituated wild population of group-living cooperatively breeding birds, the southern pied babbler . We find that close kin neighbors are beneficial. Territories overlap more when neighboring groups are close kin, and these larger overlaps with kin confer larger territories (an effect not seen for overlaps with unrelated groups). Overall, territorial conflict is costly, causing significant decreases in body mass, but conflicts with kin are shorter than those conducted with nonkin. Conflicts with more familiar unrelated neighbors are also shorter, indicating these neighbors are "dear enemies." However, kinship modulates the "dear enemy" effect; even when kin are encountered less frequently, kin elicit less-aggressive responses, similar to the "dear enemy" effect. Kin selection appears to be a main influence on territorial behavior in this species. Groups derive kin-selected benefits from decreased conflicts and maintain larger territories when overlapping with kin, though not when overlapping with nonkin. More generally, it is possible that kinship extends the "dear enemy" effect in animal societies.
许多物种都会维护自己的领地，但领地之间的重叠程度以及在领地冲突中表现出的攻击性水平差异很大，即使在同一物种内部也是如此。当相邻领地的所有者是近亲时，可能会出现更大程度的领地重叠。动物也能够区分邻居和陌生人，在领地冲突中，与更熟悉的邻居发生冲突时引发的攻击性反应会更少（即“亲爱的敌人”效应）。然而，关于亲属关系和领地重叠如何影响领地冲突的研究却很匮乏，尤其是在群居物种中。在此，我们对群居且具有合作繁殖行为的野生鸟类——南方斑鸫鹛的一个习惯化种群的亲属关系、领地重叠和领地冲突进行了研究。我们发现近亲邻居是有益的。当相邻群体是近亲时，领地重叠更多，而与近亲的这些更大重叠会带来更大的领地（与非近亲群体的重叠则未出现这种效应）。总体而言，领地冲突代价高昂，会导致体重显著下降，但与亲属的冲突比与非亲属的冲突持续时间更短。与更熟悉的非亲属邻居的冲突也更短，这表明这些邻居是“亲爱的敌人”。然而，亲属关系会调节“亲爱的敌人”效应；即使较少遇到亲属，亲属引发的攻击性反应也更少，类似于“亲爱的敌人”效应。亲缘选择似乎是该物种领地行为的主要影响因素。群体从减少的冲突中获得亲缘选择带来的益处，并且在与亲属重叠时能维持更大的领地，而与非亲属重叠时则不然。更普遍地说，亲属关系有可能在动物社会中扩展“亲爱的敌人”效应。
