Evol Ecol Res 16: 121-132 (2014)     Full PDF if your library subscribes.

Co-evolution of jaegers (Stercorarius spp.) and arctic lemmings (Dicrostonyx spp. and Lemmus spp.) and the formation of the jaeger guild: an hypothesis

Lise Ruffino1 and Tarja Oksanen1,2

1Department of Biology, Section of Ecology, University of Turku, Turku, Finland and  2Department of Arctic and Marine Biology, University of Tromsø — The Arctic University of Norway, Alta, Norway

Correspondence: L. Ruffino, Department of Biology, Section of Ecology, University of Turku, FI-20014 Turku, Finland.
e-mail: lisruffino@gmail.com


Background: The Fennoscandian tundra differs from other arctic regions hosting brown lemmings (Lemmus spp.) in that it supports exceptionally low numbers of avian predators. Jaegers (Stercorarius spp.) play a central role in the guild of predators exploiting lemming outbreaks, as they are long-lived and have a vast supply of marine survival resources. Collared lemmings (Dicrostonyx spp.) evolved much earlier than brown lemmings (Lemmus spp.),

Hypothesis: Lemming–vegetation dynamics and summer predation are causally interconnected. Avian predators that are adapted to exploit lemming outbreaks evolved in tundra areas where lemming–vegetation interactions generate density oscillations with a mean period short enough to provide dependable breeding resources for predators.

Predictions: Long-tailed jaegers (Stercorarius longicaudus), primarily exploiting collared lemmings, diverged from parasitic jaegers (S. parasiticus) more than 2 million years ago. Pomarine jaegers (S. pomarinus) evolved more recently in response to the emergence of regular oscillations of brown lemming populations. The current breeding distribution of jaegers should reflect the distribution of the two lemming genera, except for areas where the oscillations generated by lemming–plant interactions are too erratic to provide dependable breeding resources.

Empirical evidence: Our hypothesis accounts for the current distributions, behaviours, and ecologies of the three jaeger species. In addition, long-tailed jaegers did diverge early from other Stercorariidae. But we still do not know whether the timing of the divergence matches the evolution of collared lemmings. Evidence suggests that either: (1) Pomarine jaegers diverged from the skua (Catharacta spp.) lineage early, before skuas had developed their distinctive morphological traits; or (2) Pomarine jaegers diverged recently from great skuas (Catharacta skua) and then reverted to the ancestral jaeger morphology. Only the latter interpretation is consistent with our hypothesis, so we need to have more reliable timing of the evolution of long-tailed and Pomarine jaegers.

Keywords: Arctic, lemming–vegetation dynamics, predation, predator–prey co-evolution, tundra.

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