Extinction cascades partially estimate herbivore losses in a complete Lepidoptera-plant food web

University of California-Davis, Department of Entomology, 1 Shields Avenue, Davis, California 95616, USA.
Ecology (Impact Factor: 4.66). 08/2013; 94(8):1785-94. DOI: 10.1890/12-1075.1
Source: PubMed


The loss of species from an ecological community can have cascading effects leading to the extinction of other species. Specialist herbivores are highly diverse and may be particularly susceptible to extinction due to host plant loss. We used a bipartite food web of 900 Lepidoptera (butterfly and moth) herbivores and 2403 plant species from Central Europe to simulate the cascading effect of plant extinctions on Lepidoptera extinctions. Realistic extinction sequences of plants, incorporating red-list status, range size, and native status, altered subsequent Lepidoptera extinctions. We compared simulated Lepidoptera extinctions to the number of actual regional Lepidoptera extinctions and found that all predicted scenarios underestimated total observed extinctions but accurately predicted observed extinctions attributed to host loss (n = 8, 14%). Likely, many regional Lepidoptera extinctions occurred for reasons other than loss of host plant alone, such as climate change and habitat loss. Ecological networks can be useful in assessing a component of extinction risk to herbivores based on host loss, but further factors may be equally important.

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Available from: Florian Altermatt, Jan 21, 2015
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    • "The prospect of accelerating anthropogenic climate change has led to an increased interest in the structure and functioning of subarctic (Stahlhut et al. 2013; Vindstad et al. 2013) and arctic (Timms et al. 2013; Wirta et al. 2014) food webs, with the result that arctic parasitoid communities have been found to be surprisingly diverse (Fernandez-Triana et al. 2011; Várkonyi & Roslin 2013). These higher trophic levels are the most threatened by ongoing shrub expansion at the expense of open arctic–alpine habitats (Tape et al. 2006; Hallinger et al. 2010; Rich et al. 2013), as extinctions triggered by habitat loss necessarily proceed in a top–down direction (Komonen et al. 2000; Pearse & Altermatt 2013; Roslin et al. 2013). Therefore, the distinctness and high specialization of interactions found within the arctic–alpine component of our focal food web highlights the current dire situation of northern ecosystems: as shown by the species-distribution models of Thuiller et al. (2005) and Alsos et al. (2009, 2012), the geographical ranges of dwarf willows and many other cold-adapted plants are expected to contract significantly in the coming decades. "
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    ABSTRACT: Studies on the determinants of plant-herbivore and herbivore-parasitoid associations provide important insights into the origin and maintenance of global and local species richness. If parasitoids are specialists on herbivore niches rather than on herbivore taxa, then alternating escape of herbivores into novel niches and delayed resource tracking by parasitoids could fuel diversification at both trophic levels. We used DNA barcoding to identify parasitoids that attack larvae of seven Pontania sawfly species that induce leaf galls on eight willow species growing in subarctic and arctic-alpine habitats in three geographic locations in northern Fennoscandia, and then applied distance- and model-based multivariate analyses and phylogenetic regression methods to evaluate the hierarchical importance of location, phylogeny, and different galler niche dimensions on parasitoid host use. We found statistically significant variation in parasitoid communities across geographic locations and willow host species, but the differences were mainly quantitative due to extensive sharing of enemies among gallers within habitat types. By contrast, the divide between habitats defined two qualitatively different network compartments, because many common parasitoids exhibited strong habitat preference. Galler and parasitoid phylogenies did not explain associations, because distantly related arctic-alpine gallers were attacked by a species-poor enemy community dominated by two parasitoid species that most likely have independently tracked the gallers' evolutionary shifts into the novel habitat. Our results indicate that barcode- and phylogeny-based analyses of food webs that span forested vs. tundra or grassland environments could improve our understanding of vertical diversification effects in complex plant-herbivore-parasitoid networks. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Molecular Ecology 09/2015; DOI:10.1111/mec.13369 · 6.49 Impact Factor
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    • "Molecular methods (Wirta et al. 2014) can also improve our ability to detect species–specific interactions and overcome sampling issues. Finally, catalogues, databases and expert knowledge may be useful to better capture all potential interactions for applications more interested in specialization of fundamental niches (Pearse and Altermatt 2013). However, in addition to potentially changing the biological interpretation, all complementary information will likely only improve data "
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    Oikos 05/2015; DOI:10.1111/oik.02256 · 3.44 Impact Factor
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    • "The loss of even a single important food can have severe impacts. For example, Pearse and Altermatt (2013) used simulations and field data to demonstrate that loss of their host plant was a significant driver for extinctions of specialist herbivores among the Lepidoptera. Similarly, LoGiudice (2006) reported that the loss of American chestnut (Castanea dentata) was likely a contributing factor to extirpations and reductions of Allegheny woodrat (Neotoma magister) populations. "
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    Ecology and Evolution 05/2014; 4(10). DOI:10.1002/ece3.1082 · 2.32 Impact Factor
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