Local or global? Biogeography of some primitive Lepidoptera in New Zealand

Abstract

Distribution maps are presented for 30 species of small forest moths representing two genera of Micropterigidae and one genus of Mnesarchaeidae. Evolutionary patterns are interpreted by means of the panbiogeographic method in order to seek a relationship between dispersal patterns within New Zealand and the overseas links of the taxa in question. It is established that different evolutionary lines indeed exhibit different geographic dispersal patterns within New Zealand. Moreover, certain characteristics of these patterns can be attributed to the overseas affinities of the groups, i.e., groups of organisms with New Caledonian or Australian affinities have a western disjunct pattern, whereas those with circum-Pacific affinities have a different pattern in which the taxa occupying a basal position in the phylogeny are to be found in the eastern South Island. However, both groups have overlapping centres of diversity, particularly in NW Nelson.     

Mopane diaspores are not dispersed by epizoochory

The mode of dispersal of the diaspores of Colophospermum mopane has always been ascribed to epizoochory due the slightly sticky nature of mopane diaspores. The stickiness results from the plentiful supply of resinous compounds in developing structures on a mopane plant. Epizoochory as the mode of dispersal for both seeds which had the pod removed and diaspores of C. mopane is disproved, and experimentation shows the most likely agents of dispersal of mopane diaspores to be water and wind.     

A process‐based metacommunity framework linking local and regional scale community ecology

The metacommunity concept has the potential to integrate local and regional dynamics within a general community ecology framework. To this end, the concept must move beyond the discrete archetypes that have largely defined it (e.g. neutral vs. species sorting) and better incorporate local scale species interactions and coexistence mechanisms. Here, we present a fundamental reconception of the framework that explicitly links local coexistence theory to the spatial processes inherent to metacommunity theory, allowing for a continuous range of competitive community dynamics. These dynamics emerge from the three underlying processes that shape ecological communities: (1) density‐independent responses to abiotic conditions, (2) density‐dependent biotic interactions and (3) dispersal. Stochasticity is incorporated in the demographic realisation of each of these processes. We formalise this framework using a simulation model that explores a wide range of competitive metacommunity dynamics by varying the strength of the underlying processes. Using this model and framework, we show how existing theories, including the traditional metacommunity archetypes, are linked by this common set of processes. We then use the model to generate new hypotheses about how the three processes combine to interactively shape diversity, functioning and stability within metacommunities.     

Between a rock and a hard place: adaptive sensing and site‐specific dispersal

Environmental variability can lead to dispersal: why stay put if it is better elsewhere? Without clues about local conditions, the optimal strategy is often to disperse a set fraction of offspring. Many habitats contain environmentally differing sub‐habitats. Is it adaptive for individuals to sense in which sub‐habitat they find themselves, using environmental clues, and respond plastically by altering the dispersal rates? This appears to be done by some plants which produce dimorphic seeds with differential dispersal properties in response to ambient temperature. Here we develop a mathematical model to show, that in highly variable environments, not only does sensing promote plasticity of dispersal morph ratio, individuals who can sense their sub‐habitat and respond in this way have an adaptive advantage over those who cannot. With a rise in environmental variability due to climate change, our understanding of how natural populations persist and respond to changes has become crucially important.     

The functional roles of species in metacommunities,as revealed by metanetwork analyses of bird–plant frugivory networks

Understanding how biodiversity and interaction networks change across environmental gradients is a major challenge in ecology. We integrated metacommunity and metanetwork perspectives to test species’ functional roles in bird–plant frugivory interactions in a fragmented forest landscape in Southwest China, with consequences for seed dispersal. Availability of fruit resources both on and under trees created vertical feeding stratification for frugivorous birds. Bird–plant interactions involving birds feeding only on‐the‐tree or both on and under‐the‐tree (shared) had a higher centrality and contributed more to metanetwork organisation than interactions involving birds feeding only under‐the‐tree. Moreover, bird–plant interactions associated with large‐seeded plants disproportionately contributed to metanetwork organisation and centrality. Consequently, on‐the‐tree and shared birds contributed more to metanetwork organisation whereas under‐the‐tree birds were more involved in local processes. We would expect that species’ roles in the metanetwork will translate into different conservation values for maintaining functioning of seed‐dispersal networks.