Finding NEMO: nestedness engendered by mutualistic organization in anemonefish and their hosts

Abstract

The interaction structure of mutualistic relationships, in terms of relative specialization of the partners, is important to understanding their ecology and evolution. Analyses of the mutualistic interaction between anemonefish and their host sea anemones show that the relationship is highly nested in structure, generalist species interacting with one another and specialist species interacting mainly with generalists. This supports the hypothesis that the configuration of mutualistic interactions will tend towards nestedness. In this case, the structure of the interaction is at a much larger scale than previously hypothesized, across more than 180 degrees of longitude and some 60 degrees of latitude, probably owing to the pelagic dispersal capabilities of these species in a marine environment. Additionally, we found weak support for the hypothesis that geographically widespread species should be more generalized in their interactions than species with small ranges. This study extends understanding of the structure of mutualistic relationships into previously unexplored taxonomic and physical realms, and suggests how nestedness analysis can be applied to the conservation of obligate species interactions.

Hybridisation and diversification in the adaptive radiation of clownfishes

“…We find that both hybrids 2 and 3 inherited their mitochondrial genes from A. akallopisos. The plastid sequence of hybrid 1 is similar to A. perideraion and A. leucokranos, as already proposed [20], derives from A. chrysopterus. Moreover, in the mitochondrial tree, A. leucokranos clusters with A. chrysopterus sampled from the Solomon Islands, the origin of A. leucokranos ( Figure 5).…”

“…The relative position of the ephippium clade changes radically between the two datasets, which suggests the occurrence of hybridisation in the timeframe of node 8 ( Figure 2). While this node is not basal to all clownfishes, it is ancestral to 24 of the 28 species (30 described species minus A. leucokranos and A. thiellei which were likely described from hybrid material [20]). This clade represents a major shift in diversification rate with a 2.5-fold increase compared to the diversification rate of Pomacentridae [22,23].…”

“…Since their taxonomic descriptions, the species status of A. leucokranos and A. thiellei has been questioned [20]. Indeed, heterospecific pairs have been observed in the wild and fish with similar phenotype can be produced in aquaria by hybrid crosses [17].…”

Are insect pollinators more generalist than insect herbivores?

“…This idea is commonly held in the literature dealing with community-level interaction networks but has not been properly tested yet. Indeed, the nested structure of mutualistic networks Guimaraes et al 2007b;Ollerton et al 2007) implies the presence of numerous generalist species, interacting with each other and forming a core to which specialized species bind. Although less studied, the structure of antagonistic bipartite networks tends to be described as compartmentalized (Prado & Lewinsohn 2004;Lewinsohn et al 2006), i.e.…”

Ecological interaction networks: prospects and pitfalls

“…Food webs, however, have also a horizontal dimension: species of the same or adjacent trophic levels interact in various ways. These interactions are rarely random but constraint in various ways by the ecology and evolutionary history of the interacting species Ollerton et al 2007). Interaction (often termed mutualistic) networks are a tool to visualize and to study the relationships between interacting species across and within trophic levels .…”