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Benjamin B Normark - One of the best experts on this subject based on the ideXlab platform.
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nonadaptive host use specificity in tropical armored Scale Insects
Ecology and Evolution, 2020Co-Authors: Daniel A Peterson, Takao Itioka, Geoffrey E Morse, Nate B Hardy, Jiufeng Wei, Benjamin B NormarkAbstract:Most herbivorous Insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade-offs on alternative host plants, yet the evidence of such trade-offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population-genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored Scale Insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more-specialized species occur on fewer of their potential hosts than do less-specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored Scale Insects at two widely separated sites, more-specialized species do not appear to outperform more generalist species.
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nonadaptive radiation pervasive diet specialization by drift in Scale Insects
Evolution, 2016Co-Authors: Nate B Hardy, Daniel A Peterson, Benjamin B NormarkAbstract:At least half of metazoan species are herbivorous Insects. Why are they so diverse? Most herbivorous Insects feed on few plant species, and adaptive host specialization is often invoked to explain their diversification. Nevertheless, it is possible that the narrow host ranges of many herbivorous Insects are nonadaptive. Here, we test predictions of this hypothesis with comparative phylogenetic analyses of Scale Insects, a group for which there appear to be few host-use trade-offs that would select against polyphagy, and for which passive wind-dispersal should make host specificity costly. We infer a strong positive relationship between host range and diversification rate, and a marked asymmetry in cladogenetic changes in diet breadth. These results are consonant with a system of pervasive nonadaptive host specialization in which small, drift- and extinction-prone populations are frequently isolated from persistent and polyphagous source populations. They also contrast with the negative relationship between diet breadth and taxonomic diversification that has been estimated in butterflies, a disparity that likely stems from differences in the average costs and benefits of host specificity and generalism in Scale Insects versus butterflies. Our results indicate the potential for nonadaptive processes to be important to diet-breadth evolution and taxonomic diversification across herbivorous Insects.
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nonadaptive radiation pervasive diet specialization by drift in Scale Insects
bioRxiv, 2016Co-Authors: Nate B Hardy, Daniel A Peterson, Benjamin B NormarkAbstract:At least half of metazoan species are herbivorous Insects. Why are they so diverse? Most herbivorous Insects feed on few plant species, and adaptive host specialization is often invoked to explain their diversification. Nevertheless, it is possible that the narrow host ranges of many herbivorous Insects are non-adaptive. Here, we test predictions of this hypothesis with comparative phylogenetic analyses of Scale Insects, a group for which there appears to be few host-use tradeoffs that would select against polyphagy, and for which passive wind-dispersal should make host specificity costly. We infer a strong positive relationship between host range and diversification rate, and a marked asymmetry in cladogenetic changes in diet breadth. These results are consonant with a system of pervasive non-adaptive host specialization in which small, drift- and extinction-prone populations are frequently isolated from persistent and polyphagous source populations. They also contrast with the negative relationship between diet breadth and taxonomic diversification that has been estimated in butterflies, a disparity which likely stems from differences in the average costs and benefits of host specificity and generalism in Scale Insects vs. butterflies. Our results indicate the potential for non-adaptive processes to be important to diet-breadth evolution and taxonomic diversification across herbivorous Insects.
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armored Scale Insects hemiptera diaspididae of san lorenzo national park panama with descriptions of two new species
Annals of The Entomological Society of America, 2014Co-Authors: Benjamin B Normark, Geoffrey E Morse, Amanda Krewinski, Akiko OkusuAbstract:ABSTRACT Armored Scale Insects include invasive economic pests that have been widely studied in human-altered habitats but have received less attention in natural habitats. Although armored Scale Insects are nearly ubiquitous associates of woody plants, they generally go uncollected in general surveys because they are not susceptible to mass collecting techniques, such as fogging, beating, or trapping. San Lorenzo National Park in Panama was the subject of a recent high-profile effort to quantify the arthropod diversity in a tropical forest (Basset et al. 2012). Here, we contribute to understanding the biodiversity of this classic site by reporting the armored Scale insect species we found there in August 2010. We found that, unlike other rainforest canopy taxa, the armored Scale insect fauna is dominated by highly polyphagous cosmopolitan pests. However, we also found new species, and we describe two of them here: Furcaspis douglorum Okusu & Normark n. sp. and Hemiberlesia andradae Okusu & Normark n. sp....
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the nutrient supplying capabilities of uzinura an endosymbiont of armoured Scale Insects
Environmental Microbiology, 2013Co-Authors: Zakee L Sabree, Akiko Okusu, Charlie Y Huang, Nancy A Moran, Benjamin B NormarkAbstract:Summary An emerging common physiological feature of plant sap-feeding Insects is the presence of bacterial endosymbionts capable of providing essential nutrients to their host. These microbial partners are inviable outside of specialized host tissues, and therefore a cultivation-independent approach, namely high-throughput next-generation genome sequencing, can be used to characterize their gene content and metabolic potential. To this end, we sequenced the first complete genome of the obligate endosymbiont, Candidatus ‘Uzinura diaspidicola’, of armoured Scale Insects. At 263 431 bp, Uzinura has an extremely reduced genome that is composed largely of genes encoding enzymes involved in translation and amino acid biosynthesis. The tiny size of the Uzinura genome parallels that observed in some other insect endosymbionts. Despite this extreme genome reduction, the absence of a known obligate partner bacterial symbiont suggests that Uzinura alone can supply sufficient nutrients to its host.
Geoffrey E Morse - One of the best experts on this subject based on the ideXlab platform.
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nonadaptive host use specificity in tropical armored Scale Insects
Ecology and Evolution, 2020Co-Authors: Daniel A Peterson, Takao Itioka, Geoffrey E Morse, Nate B Hardy, Jiufeng Wei, Benjamin B NormarkAbstract:Most herbivorous Insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade-offs on alternative host plants, yet the evidence of such trade-offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population-genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored Scale Insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more-specialized species occur on fewer of their potential hosts than do less-specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored Scale Insects at two widely separated sites, more-specialized species do not appear to outperform more generalist species.
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armored Scale Insects hemiptera diaspididae of san lorenzo national park panama with descriptions of two new species
Annals of The Entomological Society of America, 2014Co-Authors: Benjamin B Normark, Geoffrey E Morse, Amanda Krewinski, Akiko OkusuAbstract:ABSTRACT Armored Scale Insects include invasive economic pests that have been widely studied in human-altered habitats but have received less attention in natural habitats. Although armored Scale Insects are nearly ubiquitous associates of woody plants, they generally go uncollected in general surveys because they are not susceptible to mass collecting techniques, such as fogging, beating, or trapping. San Lorenzo National Park in Panama was the subject of a recent high-profile effort to quantify the arthropod diversity in a tropical forest (Basset et al. 2012). Here, we contribute to understanding the biodiversity of this classic site by reporting the armored Scale insect species we found there in August 2010. We found that, unlike other rainforest canopy taxa, the armored Scale insect fauna is dominated by highly polyphagous cosmopolitan pests. However, we also found new species, and we describe two of them here: Furcaspis douglorum Okusu & Normark n. sp. and Hemiberlesia andradae Okusu & Normark n. sp....
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a phylogenetic analysis of armored Scale Insects hemiptera diaspididae based upon nuclear mitochondrial and endosymbiont gene sequences
Molecular Phylogenetics and Evolution, 2010Co-Authors: Jeremy C Andersen, Geoffrey E Morse, Matthew E Gruwell, Rodger A Gwiazdowski, Sharlene E Santana, Natalie M Feliciano, Benjamin B NormarkAbstract:Armored Scale Insects (Hemiptera: Diaspididae) are among the most invasive Insects in the world. They have unusual genetic systems, including diverse types of paternal genome elimination (PGE) and parthe- nogenesis. Intimate relationships with their host plants and bacterial endosymbionts make them poten- tially important subjects for the study of co-evolution. Here, we expand upon recent phylogenetic work (Morse and Normark, 2006) by analyzing armored Scale and endosymbiont DNA sequences from 125 spe- cies of armored Scale insect, represented by 253 samples and eight outgroup species. We used fragments of four different gene regions: the nuclear protein-coding gene Elongation Factor 1a (EF1a), the large ribosomal subunit (28S) rDNA, a mitochondrial region spanning parts of cytochrome oxidase I (COI) and cytochrome oxidase II (COII), and the small ribosomal subunit (16S) rDNA from the primary bacterial endosymbiont Uzinura diaspidicola. Maximum likelihood, and Bayesian analyses were performed produc- ing highly congruent topological results. A comparison of two datasets, one with and one without missing data, found that missing data had little effect on topology. Our results broadly corroborate several major features of the existing classification, although we do not find any of the subfamilies, tribes or subtribes to be monophyletic as currently constituted. Using ancestral state reconstruction we estimate that the ancestral armored Scale had the late PGE sex system, and it may as well have been pupillarial, though results differed between reconstruction methods. These results highlight the need for a complete revision of this family, and provide the groundwork for future taxonomic work in armored Scale Insects.
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phylogenetic congruence of armored Scale Insects hemiptera diaspididae and their primary endosymbionts from the phylum bacteroidetes
Molecular Phylogenetics and Evolution, 2007Co-Authors: Matthew E Gruwell, Geoffrey E Morse, Benjamin B NormarkAbstract:Abstract Insects in the sap-sucking hemipteran suborder Sternorrhyncha typically harbor maternally transmitted bacteria housed in a specialized organ, the bacteriome. In three of the four superfamilies of Sternorrhyncha (Aphidoidea, Aleyrodoidea, Psylloidea), the bacteriome-associated (primary) bacterial lineage is from the class Gammaproteobacteria (phylum Proteobacteria). The fourth superfamily, Coccoidea (Scale Insects), has a diverse array of bacterial endosymbionts whose affinities are largely unexplored. We have amplified fragments of two bacterial ribosomal genes from each of 68 species of armored Scale Insects (Diaspididae). In spite of initially using primers designed for Gammaproteobacteria, we consistently amplified sequences from a different bacterial phylum: Bacteroidetes. We use these sequences (16S and 23S, 2105 total base pairs), along with previously published sequences from the armored Scale hosts (elongation factor 1α and 28S rDNA) to investigate phylogenetic congruence between the two clades. The Bayesian tree for the bacteria is roughly congruent with that of the hosts, with 67% of nodes identical. Partition homogeneity tests found no significant difference between the host and bacterial data sets. Of thirteen Shimodaira–Hasegawa tests, comparing the original Bayesian bacterial tree to bacterial trees with incongruent clades forced to match the host tree, 12 found no significant difference. A significant difference in topology was found only when the entire host tree was compared with the entire bacterial tree. For the bacterial data set, the treelengths of the most parsimonious host trees are only 1.8–2.4% longer than that of the most parsimonious bacterial trees. The high level of congruence between the topologies indicates that these Bacteroidetes are the primary endosymbionts of armored Scale Insects. To investigate the phylogenetic affinities of these endosymbionts, we aligned some of their 16S rDNA sequences with other known Bacteroidetes endosymbionts and with other similar sequences identified by BLAST searches. Although the endosymbionts of armored Scales are only distantly related to the endosymbionts of the other sternorrhynchan Insects, they are closely related to bacteria associated with eriococcid and margarodid Scale Insects, to cockroach and auchenorrynchan endosymbionts (Blattabacterium and Sulcia), and to male-killing endosymbionts of ladybird beetles. We propose the name “Candidatus Uzinura diaspidicola” for the primary endosymbionts of armored Scale Insects.
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a molecular phylogenetic study of armoured Scale Insects hemiptera diaspididae
Systematic Entomology, 2005Co-Authors: Geoffrey E Morse, Benjamin B NormarkAbstract:Armoured Scale Insects are economically important parasites of woody plants and grasses. They are promising subjects for the evolutionary study of physiology (no complete gut), genetics (chimerism, paternal genome elimination, frequent parthenogenesis) and coevolution (with host plants, para- sitoids, Septobasidium fungi, endosymbiotic bacteria). Little phylogenetic work has been accomplished with armoured Scales, and uncertainty surrounds their classification. Here, we report the phylogenetic results of Bayesian and parsimony analyses of 705 base pairs of Elongation Factor 1a and 660 base pairs of 28S from eighty-nine species of armoured Scale Insects, representing forty-seven genera and five tribes in the subfamilies Diaspidinae and Aspidiotinae, together with two outgroups. 28S was aligned based on a secondary structural model. Our results broadly corroborate the major features of the existing classification, although we do not find perfect monophyly of any of the traditionally recognized subfamilies or tribes. The subfamily Aspidiotinae is paraphyletic with respect to the subfamily Diaspidinae. Diaspidinae consists of two main clades that only roughly corres- pond to the tribes Lepidosaphidini and Diaspidini. Diaspidini is nearly mono- phyletic, except that it includes a single aspidiotine species. Other members of the tribe Aspidiotini form a clade, except that the clade includes a single species of Leucaspidini and excludes Maskellia and Pseudaonidia. Our results weakly sup- port the hypothesis that the most recent common ancestor of the Diaspididae had adult females that were permanently enclosed within the derm of the second instar (the pupillarial habit) and had diploid adult males that eliminated their paternal genomes during spermatogenesis (late paternal genome elimination).
Nate B Hardy - One of the best experts on this subject based on the ideXlab platform.
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nonadaptive host use specificity in tropical armored Scale Insects
Ecology and Evolution, 2020Co-Authors: Daniel A Peterson, Takao Itioka, Geoffrey E Morse, Nate B Hardy, Jiufeng Wei, Benjamin B NormarkAbstract:Most herbivorous Insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade-offs on alternative host plants, yet the evidence of such trade-offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population-genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored Scale Insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more-specialized species occur on fewer of their potential hosts than do less-specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored Scale Insects at two widely separated sites, more-specialized species do not appear to outperform more generalist species.
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nonadaptive radiation pervasive diet specialization by drift in Scale Insects
Evolution, 2016Co-Authors: Nate B Hardy, Daniel A Peterson, Benjamin B NormarkAbstract:At least half of metazoan species are herbivorous Insects. Why are they so diverse? Most herbivorous Insects feed on few plant species, and adaptive host specialization is often invoked to explain their diversification. Nevertheless, it is possible that the narrow host ranges of many herbivorous Insects are nonadaptive. Here, we test predictions of this hypothesis with comparative phylogenetic analyses of Scale Insects, a group for which there appear to be few host-use trade-offs that would select against polyphagy, and for which passive wind-dispersal should make host specificity costly. We infer a strong positive relationship between host range and diversification rate, and a marked asymmetry in cladogenetic changes in diet breadth. These results are consonant with a system of pervasive nonadaptive host specialization in which small, drift- and extinction-prone populations are frequently isolated from persistent and polyphagous source populations. They also contrast with the negative relationship between diet breadth and taxonomic diversification that has been estimated in butterflies, a disparity that likely stems from differences in the average costs and benefits of host specificity and generalism in Scale Insects versus butterflies. Our results indicate the potential for nonadaptive processes to be important to diet-breadth evolution and taxonomic diversification across herbivorous Insects.
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nonadaptive radiation pervasive diet specialization by drift in Scale Insects
bioRxiv, 2016Co-Authors: Nate B Hardy, Daniel A Peterson, Benjamin B NormarkAbstract:At least half of metazoan species are herbivorous Insects. Why are they so diverse? Most herbivorous Insects feed on few plant species, and adaptive host specialization is often invoked to explain their diversification. Nevertheless, it is possible that the narrow host ranges of many herbivorous Insects are non-adaptive. Here, we test predictions of this hypothesis with comparative phylogenetic analyses of Scale Insects, a group for which there appears to be few host-use tradeoffs that would select against polyphagy, and for which passive wind-dispersal should make host specificity costly. We infer a strong positive relationship between host range and diversification rate, and a marked asymmetry in cladogenetic changes in diet breadth. These results are consonant with a system of pervasive non-adaptive host specialization in which small, drift- and extinction-prone populations are frequently isolated from persistent and polyphagous source populations. They also contrast with the negative relationship between diet breadth and taxonomic diversification that has been estimated in butterflies, a disparity which likely stems from differences in the average costs and benefits of host specificity and generalism in Scale Insects vs. butterflies. Our results indicate the potential for non-adaptive processes to be important to diet-breadth evolution and taxonomic diversification across herbivorous Insects.
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large population size predicts the distribution of asexuality in Scale Insects
Evolution, 2013Co-Authors: Nate B Hardy, Laura Ross, Akiko Okusu, Benjamin B NormarkAbstract:Understanding why some organisms reproduce by sexual reproduction while others can reproduce asexually remains an important unsolved problem in evolutionary biology. Simple demography suggests that asexuals should outcompete sexually reproducing organisms, because of their higher intrinsic rate of increase. However, the majority of multicellular organisms have sexual reproduction. The widely accepted explanation for this apparent contradiction is that asexual lineages have a higher extinction rate. A number of models have indicated that population size might play a crucial role in the evolution of asexuality. The strength of processes that lead to extinction of asexual species is reduced when population sizes get very large, so that the long-term advantage of sexual over asexual reproduction may become negligible. Here, we use a comparative approach using Scale Insects (Coccoidea, Hemiptera) to show that asexuality is indeed more common in species with larger population density and geographic distribution and we also show that asexual species tend to be more polyphagous. We discuss the implication of our findings for previously observed patterns of asexuality in agricultural pests.
Takao Itioka - One of the best experts on this subject based on the ideXlab platform.
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nonadaptive host use specificity in tropical armored Scale Insects
Ecology and Evolution, 2020Co-Authors: Daniel A Peterson, Takao Itioka, Geoffrey E Morse, Nate B Hardy, Jiufeng Wei, Benjamin B NormarkAbstract:Most herbivorous Insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade-offs on alternative host plants, yet the evidence of such trade-offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population-genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored Scale Insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more-specialized species occur on fewer of their potential hosts than do less-specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored Scale Insects at two widely separated sites, more-specialized species do not appear to outperform more generalist species.
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phylogeography of the coccus Scale Insects inhabiting myrmecophytic macaranga plants in southeast asia
Population Ecology, 2010Co-Authors: Shouhei Ueda, Sweepeck Quek, Kaori Murase, Takao Itioka, Takao ItinoAbstract:Comparative historical biogeography of multiple symbionts occurring on a common host taxa can shed light on the processes of symbiont diversification. Myrmecophytic Macaranga plants are associated with the obligate mutualistic symbionts: Crematogaster (subgenus Decacrema) ants and Coccus Scale Insects. We conduct phylogeographic analyses based on mitochondrial cytochrome oxidase I (COI) from 253 Scale Insects collected from 15 locations in Borneo, Malaya and Sumatra, to investigate the historical biogeography of the Scales, and then to draw comparisons with that of the symbiotic, but independently dispersing, Decacrema ants which are not specific to different Coccus lineages. Despite the different mode of ancient diversification, reconstruction of ancestral area and age estimation on the Coccus phylogeny showed that the Scales repeatedly migrated between Borneo and Malaya from Pliocene to Pleistocene, which is consistent with the Decacrema ants. Just as with the ants, the highest number of lineages in the Scale Insects was found in northern northwest Borneo, suggesting that these regions were rainforest refugia during cool dry phases of the Pleistocene. Overall, general congruence between the Plio–Pleistocene diversification histories of the symbiotic Scales and ants suggests that they experienced a common history of extinction/migration despite their independent mode of dispersal and host-colonization.
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an ancient tripartite symbiosis of plants ants and Scale Insects
Proceedings of The Royal Society B: Biological Sciences, 2008Co-Authors: Shouhei Ueda, Sweepeck Quek, Kaori Murase, Takao Itioka, Keita Inamori, Yumiko Sato, Takao ItinoAbstract:In the Asian tropics, a conspicuous radiation of Macaranga plants is inhabited by obligately associated Crematogaster ants tending Coccus (Coccidae) Scale Insects, forming a tripartite symbiosis. Recent phylogenetic studies have shown that the plants and the ants have been codiversifying over the past 16–20 million years (Myr). The prevalence of coccoids in ant–plant mutualisms suggest that they play an important role in the evolution of ant–plant symbioses. To determine whether the Scale Insects were involved in the evolutionary origin of the mutualism between Macaranga and Crematogaster ,w e constructed a cytochrome oxidase I (COI ) gene phylogeny of the Scale Insects collected from myrmecophytic Macaranga and estimated their time of origin based on a COI molecular clock. The minimum age of the associated Coccus was estimated to be half that of the ants, at 7–9 Myr, suggesting that they were latecomers in the evolutionary history of the symbiosis. Crematogaster mitochondrial DNA (mtDNA) lineages did not exhibit specificity towards Coccus mtDNA lineages, and the latter was not found to be specific towards Macaranga taxa, suggesting that patterns of associations in the Scale Insects are dictated by opportunity rather than by specialized adaptations to host plant traits.
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settling site selection and survival of two Scale Insects ceroplastes rubens and c ceriferus on citrus trees
Population Ecology, 1991Co-Authors: Takao Itioka, Tamiji InoueAbstract:We studied settling-site selection and the resulting survival of two sessile Scale Insects,Ceroplastes rubens andC. ceriferus, in the citrus tree,Citrus unshiu, in central Japan.
Daniel A Peterson - One of the best experts on this subject based on the ideXlab platform.
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nonadaptive host use specificity in tropical armored Scale Insects
Ecology and Evolution, 2020Co-Authors: Daniel A Peterson, Takao Itioka, Geoffrey E Morse, Nate B Hardy, Jiufeng Wei, Benjamin B NormarkAbstract:Most herbivorous Insects are diet specialists in spite of the apparent advantages of being a generalist. This conundrum might be explained by fitness trade-offs on alternative host plants, yet the evidence of such trade-offs has been elusive. Another hypothesis is that specialization is nonadaptive, evolving through neutral population-genetic processes and within the bounds of historical constraints. Here, we report on a striking lack of evidence for the adaptiveness of specificity in tropical canopy communities of armored Scale Insects. We find evidence of pervasive diet specialization, and find that host use is phylogenetically conservative, but also find that more-specialized species occur on fewer of their potential hosts than do less-specialized species, and are no more abundant where they do occur. Of course local communities might not reflect regional diversity patterns. But based on our samples, comprising hundreds of species of hosts and armored Scale Insects at two widely separated sites, more-specialized species do not appear to outperform more generalist species.
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nonadaptive radiation pervasive diet specialization by drift in Scale Insects
Evolution, 2016Co-Authors: Nate B Hardy, Daniel A Peterson, Benjamin B NormarkAbstract:At least half of metazoan species are herbivorous Insects. Why are they so diverse? Most herbivorous Insects feed on few plant species, and adaptive host specialization is often invoked to explain their diversification. Nevertheless, it is possible that the narrow host ranges of many herbivorous Insects are nonadaptive. Here, we test predictions of this hypothesis with comparative phylogenetic analyses of Scale Insects, a group for which there appear to be few host-use trade-offs that would select against polyphagy, and for which passive wind-dispersal should make host specificity costly. We infer a strong positive relationship between host range and diversification rate, and a marked asymmetry in cladogenetic changes in diet breadth. These results are consonant with a system of pervasive nonadaptive host specialization in which small, drift- and extinction-prone populations are frequently isolated from persistent and polyphagous source populations. They also contrast with the negative relationship between diet breadth and taxonomic diversification that has been estimated in butterflies, a disparity that likely stems from differences in the average costs and benefits of host specificity and generalism in Scale Insects versus butterflies. Our results indicate the potential for nonadaptive processes to be important to diet-breadth evolution and taxonomic diversification across herbivorous Insects.
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nonadaptive radiation pervasive diet specialization by drift in Scale Insects
bioRxiv, 2016Co-Authors: Nate B Hardy, Daniel A Peterson, Benjamin B NormarkAbstract:At least half of metazoan species are herbivorous Insects. Why are they so diverse? Most herbivorous Insects feed on few plant species, and adaptive host specialization is often invoked to explain their diversification. Nevertheless, it is possible that the narrow host ranges of many herbivorous Insects are non-adaptive. Here, we test predictions of this hypothesis with comparative phylogenetic analyses of Scale Insects, a group for which there appears to be few host-use tradeoffs that would select against polyphagy, and for which passive wind-dispersal should make host specificity costly. We infer a strong positive relationship between host range and diversification rate, and a marked asymmetry in cladogenetic changes in diet breadth. These results are consonant with a system of pervasive non-adaptive host specialization in which small, drift- and extinction-prone populations are frequently isolated from persistent and polyphagous source populations. They also contrast with the negative relationship between diet breadth and taxonomic diversification that has been estimated in butterflies, a disparity which likely stems from differences in the average costs and benefits of host specificity and generalism in Scale Insects vs. butterflies. Our results indicate the potential for non-adaptive processes to be important to diet-breadth evolution and taxonomic diversification across herbivorous Insects.
