Do asynchronies in extinction debt affect the structure of trophic networks? A case study of antagonistic butterfly larvae–plant networks

Guardiola M., Stefanescu C., Rod F., Pino J. (2018) Do asynchronies in extinction debt affect the structure of trophic networks? A case study of antagonistic butterfly larvae–plant networks. Oikos. 127: 803-813.
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Doi: 10.1111/oik.04536

Resum:

Habitat loss and fragmentation affect species richness in fragmented habitats and can lead to immediate or time-delayed species extinctions. Asynchronies in extinction and extinction debt between interacting species may have severe effects on ecological networks. However, these effects remain largely unknown. We evaluated the effects of habitat patch and landscape changes on antagonistic butterfly larvae–plant trophic networks in Mediterranean grasslands in which previous studies had shown the existence of extinction debt in plants but not in butterflies. We sampled current species richness of habitat-specialist and generalist butterflies and vascular plants in 26 grasslands. We assessed the direct effects of historical and current patch and landscape characteristics on species richness and on butterfly larvae–plant trophic network metrics and robustness. Although positive species- and interactions–area relationships were found in all networks, structure and robustness was only affected by patch and landscape changes in networks involving the subset of butterfly specialists. Larger patches had more species (butterflies and host plants) and interactions but also more compartments, which decreased network connectance but increased network stability. Moreover, most likely due to the rescue effect, patch connectivity increased host-plant species (but not butterfly) richness and total links, and network robustness in specialist networks. On the other hand, patch area loss decreased robustness in specialist butterfly larvae–plant networks and made them more prone to collapse against host plant extinctions. Finally, in all butterfly larvae–plant networks we also detected a past patch and landscape effect on network asymmetry, which indicates that there were different extinction rates and extinction debts for butterflies and host plants. We conclude that asynchronies in extinction and extinction debt in butterfly–plant networks provoked by patch and landscape changes caused changes in species richness and network links in all networks, as well as changes in network structure and robustness in specialist networks. © 2017 The Authors

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Diversity of insect pollinators in the Iberian Peninsula [Diversidad de insectos polinizadores en la península ibérica]

Stefanescu C., Aguado L.O., Asís J.D., Baños-Picńn L., Cerdá X., Marcos García M.Á., Micń E., Ricarte A., Tormos J. (2018) Diversity of insect pollinators in the Iberian Peninsula [Diversidad de insectos polinizadores en la península ibérica]. Ecosistemas. 27: 9-22.
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Doi: 10.7818/ECOS.1391

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Numerous observations and studies that have been carried out in recent decades show that, in addition to bees ((Hymenoptera; Anthophila), other groups of insects play a major role in entomophilous pollination. This article reviews the information and literature available on the contribution of the main groups of pollinators that traditionally have been considered as "secondary": beetles, butterflies and moths, dipterans, wasps and ants. For each of these groups a common outline is followed, with a brief introduction, a summary of the basic characteristics - both morphological and behavioral - in relation to pollination, their effectiveness as pollinators and their conservation status in the Iberian Peninsula. This review highlights the importance of all these groups in entomophilous pollination and the need to include them in comprehensive studies on this phenomenon. Although data are generally very limited, there is clear evidence of a general decline in most of these groups which calls for a pressing need to improve knowledge about their population trends. © 2018. Los Autores.

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Physiological differences between female limited, alternative life history strategies: The Alba phenotype in the butterfly Colias croceus

Woronik A., Stefanescu C., Käkelä R., Wheat C.W., Lehmann P. (2018) Physiological differences between female limited, alternative life history strategies: The Alba phenotype in the butterfly Colias croceus. Journal of Insect Physiology. 107: 257-264.
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Doi: 10.1016/j.jinsphys.2018.03.008

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Across a wide range of taxa, individuals within populations exhibit alternative life history strategies (ALHS) where their phenotypes dramatically differ due to divergent investments in growth, reproduction and survivorship, with the resulting trade-offs directly impacting Darwinian fitness. Though the maintenance of ALHS within populations is fairly well understood, little is known regarding the physiological mechanisms that underlie ALHS and how environmental conditions can affect the evolution and expression of these phenotypes. One such ALHS, known as Alba, exists within females of many species in the butterfly genus Colias. Previous works in New World species not only found that female morphs differ in their wing color due to a reallocation of resources away from the synthesis of wing pigments to other areas of development, but also that temperature played an important role in these trade-offs. Here we build on previous work conducted in New World species by measuring life history traits and conducting lipidomics on individuals reared at hot and cold temperatures in the Old World species Colias croceus. Results suggest that the fitness of Alba and orange morphs likely varies with rearing temperature, where Alba females have higher fitness in cold conditions and orange in warm. Additionally shared traits between Old and New World species suggest the Alba mechanism is likely conserved across the genus. Finally, in the cold treatment we observe an intermediate yellow morph that may have decreased fitness due to slower larval development. This cost may manifest as disruptive selection in the field, thereby favoring the maintenance of the two discrete morphs. Taken together these results add insights into the evolution of, and the selection on, the Alba ALHS. © 2018 Elsevier Ltd

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Applicability of butterfly transect counts to estimate species richness in different parts of the palaearctic region

Zhang C., Harpke A., Kühn E., Páramo F., Settele J., Stefanescu C., Wiemers M., Zhang Y., Schweiger O. (2018) Applicability of butterfly transect counts to estimate species richness in different parts of the palaearctic region. Ecological Indicators. 95: 735-740.
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Doi: 10.1016/j.ecolind.2018.08.027

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Transect counts are one of the most popular approaches to assess and monitor butterfly diversity, especially with the background of biodiversity loss. This method was developed in Europe, but its transferability is seldom tested across the world. To assess transferability, we compared butterfly richness estimates based on transect counts in Spain, Germany and central China, a region with a considerably different biogeographic history and more diverse butterfly fauna compared to Europe. We found that the efficiency of transect counts was much lower in China than in the other two regions. Apart from the fact that traditional transect counts may undersample canopy species which are predominant in central China, higher efficiency in Europe may be primarily attributed to different patterns of butterfly richness likely caused by different biogeographic and anthropogenic land-use history. Our results highlight that great caution is needed when transect count methods are transferred to other regions of the world, especially to particularly species rich areas with a high number of rare species. Low detectability of certain species can substantially mask species richness estimates, and we suggest to carefully adapt sampling effort and perhaps combine transect counts with other methods to ensure more realistic assessment of species richness in such regions. © 2018

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