From endogenous to exogenous pattern formation: Invasive plant species changes the spatial distribution of a native ant

Invasive species are a significant threat to global biodiversity, but our understanding of how invasive species impact native communities across space and time remains limited. Based on observations in an old field in Southeast Michigan spanning 35 years, our study documents significant impacts of habitat change, likely driven by the invasion of the shrub, Elaeagnus umbellata, on the nest distribution patterns and population demographics of a native ant species, Formica obscuripes. Landcover change in aerial photographs indicates that E. umbellata expanded aggressively, transforming a large proportion of the original open field into dense shrubland. By comparing the ant’s landcover preferences before and after the invasion, we demonstrate that this species experienced a significant unfavorable change in its foraging areas. We also find that shrub landcover significantly moderates aggression between nests, suggesting nests are more related where there is more E. umbellata. This may represent a shift in reproductive strategy from queen flights, reported in the past, to asexual nest budding. Our results suggest that E. umbellata may affect the spatial distribution of F. obscuripes by shifting the drivers of nest pattern formation from an endogenous process (queen flights), which led to a uniform pattern, to a process that is both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. The number and sizes of F. obscuripes nests in our study site are projected to decrease in the next 40 years, although further study of this population’s colony structures is needed to understand the extent of this decrease. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.Invasive species are a threat to global biodiversity, but our understanding of how they impact native communities across space and time remains limited. We compared the spatial distribution of a population of native ant Formica obscuripes in SE Michigan between 1980 and 2015, during which the invasive shrub Elaeagnus umbellata changed the dominant landcover from open field to shrubland. Analyses of ant habitat preference and aggressivity suggest that this landcover change caused the nest pattern formation process to shift from endogenous (reproductive queen flights) that led to a uniform pattern, to both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. Results of a stage‐structured model suggest that the ant population may be declining. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136690/1/gcb13671.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136690/2/gcb13671_am.pd

Ecological autocatalysis:A central principle in ecosystem organization?

Ecosystems comprise flows of energy and materials, structured by organisms and their interactions. Important generalizations have emerged in recent decades about conversions by organisms of energy (metabolic theory of ecology) and materials (ecological stoichiometry). However, these new insights leave a key question about ecosystems inadequately addressed: are there basic organizational principles that explain how the interaction structure among species in ecosystems arises? Here we integrate recent contributions to the understanding of how ecosystem organization emerges through ecological autocatalysis (EA), in which species mutually benefit through self-reinforcing circular interaction structures. We seek to generalize the concept of EA by integrating principles from community and ecosystem ecology. We discuss evidence suggesting that ecological autocatalysis is facilitated by resource competition and natural selection, both central principles in community ecology. Furthermore, we suggest that pre-emptive resource competition by consumers and plant resource diversity drive the emergence of autocatalytic loops at the ecosystem level. Subsequently, we describe how interactions between such autocatalytic loops can explain pattern and processes observed at the ecosystem scale, and summarize efforts to model different aspect of the phenomenon. We conclude that EA is a central principle that forms the backbone of the organization in systems ecology, analogous to autocatalytic loops in systems chemistry.</p

Self-organization, collective decision making and resource exploitation strategies in social insects

05.65.+b Self-organized systems, 05.10.Ln Monte Carlo methods,