Sonja J. Scheffer

Repeated climate-linked host shifts have promoted diversification in a temperate clade of leaf-mining flies

A central but little-tested prediction of “escape and radiation” coevolution is that colonization of novel, chemically defended host plant clades accelerates insect herbivore diversification. That theory, in turn, exemplifies one side of a broader debate about the relative influence on clade dynamics of intrinsic (biotic) vs. extrinsic (physical-environmental) forces. Here, we use a fossil-calibrated molecular chronogram to compare the effects of a major biotic factor (repeated shift to a chemically divergent host plant clade) and a major abiotic factor (global climate change) on the macroevolutionary dynamics of a large Cenozoic radiation of phytophagous insects, the leaf-mining fly genus Phytomyza (Diptera: Agromyzidae). We find one of the first statistically supported examples of consistently elevated net diversification accompanying shift to new plant clades. In contrast, we detect no significant direct effect on diversification of major global climate events in the early and late Oligocene. The broader paleoclimatic context strongly suggests, however, that climate change has at times had a strong indirect influence through its effect on the biotic environment. Repeated rapid Miocene radiation of these flies on temperate herbaceous asterids closely corresponds to the dramatic, climate-driven expansion of seasonal, open habitats.

Molecular evidence of cryptic species within the Liriomyza huidobrensis (Diptera: Agromyzidae).

Abstract Phylogenetic relationships among populations of the polyphagous pea leafminer, Liriomyza huidobrensis (Blanchard), were investigated using DNA sequence data. Maximum parsimony analysis of 941 bp of mitochondrial cytochrome oxidase I and II genes showed that L. huidobrensis contains two well-defined monophyletic groups, one composed of specimens from California and Hawaii and one composed of specimens from South and Central America together with populations that have been recently introduced into other parts of the world. The differentiation between the two clades within L. huidobrensis is equivalent to that seen between other agromyzid species, suggesting that L. huidobrensis as currently defined contains two cryptic species. This finding is consistent with field observations of differences in pest status and insecticide resistance between L. huidobrensis populations. Until additional studies are complete, no changes in L. huidobrensis taxonomy are proposed. However, researchers and quarantine officials may wish to consider the findings of the current study in designing research, pest management, and quarantine programs for L. huidobrensis.

Two nuclear genes confirm mitochondrial evidence of cryptic species within Liriomyza huidobrensis (Diptera: Agromyzidae).

Abstract Phylogenetic analysis using DNA sequence data from two nuclear genes was undertaken to investigate phylogeographic structure within the widespread leafmining pest Liriomyza huidobrensis (Blanchard). Parsimony analysis of 171 bp from β-tubulin (including an intron) and 921 bp from elongation factor-1α confirms previous findings from mitochondrial sequence data of deep phylogeographic structure indicative of cryptic species within L. huidobrensis. We resurrect the name L. langei Frick for the North American cryptic species and restrict the name L. huidobrensis to the South and Central American cryptic species. Results from nuclear genes also confirm previous results suggesting that recent invasions of this leafminer in many areas of the world are due to the spread of L. huidobrensis from South or Central America.

Hidden Neotropical Diversity: Greater Than the Sum of Its Parts

The diversity of tropical herbivorous insects has been explained as a direct function of plant species diversity. Testing that explanation, we reared 2857 flies from flowers and seeds of 24 species of plants from 34 neotropical sites. Samples yielded 52 morphologically similar species of flies and documented highly conserved patterns of specificity to host taxa and host parts. Widespread species of plants can support 13 species of flies. Within single populations of plants, we typically found one or more fly species specific to female flowers and multiple specialists on male flowers. We suggest that neotropical herbivorous insect diversity is not simply a function of plant taxonomic and architectural diversity, but also reflects the geographic distribution of hosts and the age and area of the neotropics.

Polymerase Chain Reaction-Restriction Fragment-Length Polymorphism Method to Distinguish Liriomyza huidobrensis from L. langei (Diptera: Agromyzidae) Applied to Three Recent Leafminer Invasions

Abstract A molecular method is presented for differentiating the morphologically cryptic leafminers Liriomyza langei Frick and L. huidobrensis (Blanchard). This method requires polymerase chain reaction (PCR) amplification of a 1031-bp region of mitochondrial cytochrome oxidase DNA followed by restriction fragment analysis using the restriction enzymes SpeI and EcoRV. SpeI cuts the mitochondrial fragment of L. langei into two fragments, but does not cut the L. huidobrensis fragment. EcoRV cuts the L. huidobrensis fragment into two fragments, but does not cut the L. langei fragment. This PCR-restriction fragment-length polymorphism (RFLP) method is faster and less costly than DNA sequencing, which is currently the only other way to differentiate these two species. We apply the method to samples from recently introduced leafminer populations in Sri Lanka, Canada, and South Africa and find that the invasive leafminer in all three locations is L. huidobrensis.

Molecular evidence of host‐associated genetic divergence in the holly leafminer Phytomyza glabricola (Diptera: Agromyzidae): apparent discordance among marker systems

Host races play a central part in understanding the role of host plant mediated divergence and speciation of phytophagous insects. Of greatest interest are host‐associated populations that have recently diverged; however, finding genetic evidence for very recent divergences is difficult because initially only a few loci are expected to evolve diagnostic differences. The holly leafminer Phytomyza glabricola feeds on two hollies, Ilex glabra and I. coriacea, that are broadly sympatric throughout most of their ranges. The leafminer is often present on both host plants and exhibits a dramatic life history difference on the two hosts, suggesting that host races may be present. We collected 1393 bp of mitochondrial cytochrome oxidase I (COI) sequence and amplified fragment length polymorphism (AFLP) data (45 polymorphic bands) from sympatric populations of flies reared from the two hosts. Phylogenetic and frequency analysis of mitochondrial COI sequence data uncovered considerable variation but no structuring by the host plant, and only limited differentiation among geographical locations. In contrast, analysis of AFLP frequency data found a significant effect with host plant, and a much smaller effect with geographical location. Likewise, neighbour‐joining analysis of AFLP data resulted in clustering by host plant. The AFLP data indicate that P. glabricola is most likely comprised of two host races. Because there were no fixed differences in mitochondrial or AFLP data, this host‐associated divergence is likely to have occurred very recently. P. glabricola therefore provides a new sympatric system for exploring the role of geography and ecological specialization in the speciation of phytophagous insects.

Mitochondrial Phylogeography of Vegetable Pest Liriomyza sativae (Diptera: Agromyzidae): Divergent Clades and Invasive Populations

Abstract The leafmining fly Liriomyza sativae Blanchard is an important polyphagous pest of vegetables crops in the United States and around the world. Phylogeographic analysis of mitochondrial cytochrome oxidase I sequence variation indicates that L. sativae harbors distinct mitochondrial clades suggestive of the presence of cryptic species. Two of the major mitochondrial clades exhibited polyphagy, with members feeding on hosts in at least three plant families. Only one of the major clades was present in introduced populations, causing total mitochondrial variation exhibited by introduced populations to be considerably reduced compared with that observed within the native range.

Lethal Interactions Between Parasites and Prey Increase Niche Diversity in a Tropical Community

Hidden Diversity Why are there so many species in the tropics? Niche partitioning by highly specialized plant species seems to be the main generator of high diversity. Condon et al. (p. 1240; see the Perspective by Godfray) show that niche partitioning can also be generated by interactions between plant resources and parasites, resulting in hyperdiverse communities. The cryptic diversity of 14 neotropical fly pollinators and 18 of their highly specific wasp parasites induced mortality partitions between multiple narrow niches. The extreme specificity of the wasp-fly relationships was initially only revealed by molecular analysis. Incorrect fly-host choice in parasitoid wasps creates multidimensional niches, generating high levels of hidden diversity. Ecological specialization should minimize niche overlap, yet herbivorous neotropical flies (Blepharoneura) and their lethal parasitic wasps (parasitoids) exhibit both extreme specialization and apparent niche overlap in host plants. From just two plant species at one site in Peru, we collected 3636 flowers yielding 1478 fly pupae representing 14 Blepharoneura fly species, 18 parasitoid species (14 Bellopius species), and parasitoid-host associations, all discovered through analysis of molecular data. Multiple sympatric species specialize on the same sex flowers of the same fly host-plant species—which suggests extreme niche overlap; however, niche partitioning was exposed by interactions between wasps and flies. Most Bellopius species emerged as adults from only one fly species, yet evidence from pupae (preadult emergence samples) show that most Bellopius also attacked additional fly species but never emerged as adults from those flies.

Molecular phylogeny and systematics of leaf‐mining flies (Diptera: Agromyzidae): delimitation of Phytomyza Fallén sensu lato and included species groups, with new insights on morphological and host‐use evolution

Abstract Phytomyza Fallén is the largest genus of leaf‐mining flies (Agromyzidae), with over 530 described species. Species of the superficially similar genus Chromatomyia Hardy have been included in Phytomyza by some authors and the status of the genus remains uncertain. Using 3076 bp of DNA sequence from three genes [cytochrome oxidase I (COI), CAD (rudimentary), phosphogluconate dehydrogenase (PGD)] and 113 exemplar species, we identified and tested the monophyly of host‐associated species groups in Phytomyza and Chromatomyia and investigated the phylogenetic relationships among these groups. Chromatomyia is polyphyletic and nested largely within Phytomyza; two small groups of species, however, are related more closely to Ptochomyza and Napomyza. Therefore, we synonymize Chromatomyiasyn.n., Ptochomyzasyn.n., and Napomyzasyn.n. with Phytomyza, recognizing Ptochomyza, Napomyza and Phytomyza sensu stricto as subgenera of Phytomyza. We recognize five major clades within Phytomyza sensu stricto that comprise the majority of species ascribed previously to Chromatomyia and Phytomyza. Many species groups recognized previously were recovered as monophyletic, or virtually so, but some (e.g. robustella and atomaria groups) required emendation. On the basis of the proposed phylogeny and recent taxonomic literature, we present a preliminary revision of 24 species groups within Phytomyza, but leave many species unplaced. Evolution of internal pupariation (within the host’s tissue), regarded as a defining character of the former Chromatomyia, is discussed with regard to the new phylogeny, and we suggest a correlation with stem or leaf midrib mining. The large size of the Phytomyza lineage and an inferred pattern of host family‐specific species radiations make it a promising candidate for the study of macroevolutionary patterns of host shift and diversification in phytophagous insects. The proposed generic synonymies necessitate a number of new combinations. The following 46 species described in Chromatomyia are transferred to Phytomyza: P. actinidiae (Sasakawa) comb.n., P. alopecuri (Griffiths) comb.n., P. arctagrostidis (Griffiths) comb.n., P. beigerae (Griffiths) comb.n., P. blackstoniae (Spencer) comb.n., P. centaurii (Spencer) comb.n., P. chamaemetabola (Griffiths) comb.n., P. cinnae (Griffiths) comb.n., P. compta (Spencer) comb.n., P. cygnicollina (Griffiths) comb.n., P. doolittlei (Spencer) comb.n., P. elgonensis (Spencer) comb.n., P. eriodictyi (Spencer) comb.n., P. flavida (Spencer) comb.n., P. fricki (Griffiths) comb.n., P. furcata (Griffiths) comb.n., P. griffithsiana (Beiger) comb.n., P. hoppiella (Spencer) comb.n., P. ixeridopsis (Griffiths) comb.n., P. kluanensis (Griffiths) comb.n., P. leptargyreae (Griffiths) comb.n., P. linnaeae (Griffiths) comb.n., P. luzulivora (Spencer) comb.n., P. mimuli (Spencer) comb.n., P. mitchelli (Spencer) comb.n., P. montella (Spencer) comb.n., P. nigrilineata (Griffiths) comb.n., P. nigrissima (Spencer) comb.n., P. orbitella (Spencer) comb.n., P. paraciliata (Godfray) comb.n., P. poae (Griffiths) comb.n., P. pseudomilii (Griffiths) comb.n., P. qinghaiensis (Gu) comb.n., P. rhaetica (Griffiths) comb.n., P. scabiosella (Beiger) comb.n., P. seneciophila (Spencer) comb.n., P. shepherdiana (Griffiths) comb.n., P. spenceriana (Griffiths) comb.n., P. styriaca (Griffiths) comb.n., P. subnigra (Spencer) comb.n., P. suikazurae (Sasakawa) comb.n., P. symphoricarpi (Griffiths) comb.n., P. syngenesiae (Hardy) comb.n., P. thermarum (Griffiths) comb.n., P. torrentium (Griffiths) comb.n. and P. tschirnhausi (Griffiths) comb.n. Furthermore, we transfer all species of Napomyza to Phytomyza, resulting in the following new combinations: P. achilleanella (Tschirnhaus) comb.n., P. acutiventris (Zlobin) comb.n., P. angulata (Zlobin) comb.n., P. arcticola (Spencer) comb.n., P. bellidis (Griffiths) comb.n., P. carotae (Spencer) comb.n., P. cichorii (Spencer) comb.n., P. curvipes (Zlobin) comb.n., P. dubia (Zlobin) comb.n., P. filipenduliphila (Zlobin) comb.n., P. flavivertex (Zlobin) comb.n., P. flavohumeralis (Zlobin) comb.n., P. genualis (Zlobin) comb.n., P. grandella (Spencer) comb.n., P. humeralis (Zlobin) comb.n., P. immanis (Spencer) comb.n., P. immerita (Spencer) comb.n., P. inquilina (Kock) comb.n., P. kandybinae (Zlobin) comb.n., P. lacustris (Zlobin) comb.n., P. laterella (Zlobin) comb.n., P. manni (Spencer) comb.n., P. maritima (Tschirnhaus) comb.n., P. merita (Zlobin) comb.n., P. mimula (Spencer) comb.n., P. minuta (Spencer) comb.n., P. montanoides (Spencer) comb.n., P. neglecta (Zlobin) comb.n., P. nigriceps (van der Wulp) comb.n., P. nugax (Spencer) comb.n., P. pallens (Spencer) comb.n., P. paratripolii (Chen & Wang) comb.n., P. plumea (Spencer) comb.n., P. plumigera (Zlobin) comb.n., P. prima (Zlobin) comb.n., P. pubescens (Zlobin) comb.n., P. schusteri (Spencer) comb.n., P. scrophulariae (Spencer) comb.n., P. suda (Spencer) comb.n., P. tanaitica (Zlobin) comb.n., P. tenuifrons (Zlobin) comb.n., P. vivida (Spencer) comb.n., P. xizangensis (Chen & Wang) comb.n. and P. zimini (Zlobin) comb.n.Phytomyza asparagi (Hering) comb.n. and P. asparagivora (Spencer) comb.n. are transferred from Ptochomyza. In Phytomyza ten new names are proposed for secondary homonyms created by generic synonymy: P. echo Winkler nom.n. for P. manni Spencer, 1986; P. californiensis Winkler nom.n. for C. montana Spencer, 1981 ; P. griffithsella Winkler nom.n. for C. griffithsi Spencer, 1986; P. vockerothi Winkler nom.n. for C. nigrella Spencer, 1986; P. kerzhneri Winkler nom.n. for N. nigricoxa Zlobin, 1993; P. asteroides Winkler nom.n. for N. tripolii Spencer, 1966; P. minimoides Winkler nom.n. for N. minima Zlobin, 1994; P. nana Winkler nom.n. for N. minutissima Zlobin, 1994; P. ussuriensis Winkler nom.n. for N. mimica Zlobin, 1994 and P. zlobini Winkler nom.n. for N. hirta Zlobin, 1994.

Evidence of Cryptic Species Within the Pest Copitarsia decolora (Guenée) (Lepidoptera: Noctuidae)

Abstract Copitarsia decolora (Guenée) is a widely distributed, highly polyphagous pest found throughout Central and South America. We examined multiple populations of C. decolora with the mitochondrial gene cytochrome oxidase I (COI). We also investigated morphological variation in adult males sampled from these populations. COI evidence suggests that C. decolora is comprised of two cryptic lineages and is paraphyletic with respect to the Chilean C. naenoides (Butler). These two lineages, which are not completely geographically isolated, display high divergence in COI sequences compared with other members of Copitarsia and other insect pest species in general. Furthermore, these lineages also possess slight morphological differences in male genitalia; however, supporting information is necessary before the taxonomy of this species is revised.