Sistematic and Phylogeny of the subtribe Megalostomina (Coleoptera Chrysomelidae).

Thesis

Summary *

The present thesis includes a taxonomic revision of the genus Megalostomis (Coleoptera: Chrysomelidae: Cryptocephalinae: Clytrini: Megalostomina), along with a cladistic analysis of the subtribe Megalostomina. It is a systematic and phylogenetic study of a Neotropical group of ?case bearer? leaf beetles, called that way because of the particular habit of their larvae, living in a portable protective case. The leaf beetles and long-horned beetles (Chrysomeloidea) together with the weevils (Curculionoidea) constitute an extraordinarily diverse group of phytophagous insects in the Order Coleoptera. Members of the subtribe Megalostomina are phytophagous in the adult stage, primarily leaf and flower feeders, but larvae of most case bearers are found in the ground litter, feeding on vegetal material, and several species are known to have myrmecophilous larvae. They constitute an important component in ecological communities of arid regions, because of their association with species of native plants (e. g., in Prosopis and Acacia) and with ants. Most species of Megalostomina occur in xeric regions of North and South of the American continent, with a high proportion of endemisms in arid regions of Argentina, particularly in the Monte region. The Megalostomina include about 140 species in seven genera: Megalostomis Chevrolat, Euryscopa Lacordaire, Coscinoptera Lacordaire, Themesia Lacordaire, Proctophana Lacordaire, Coleorozena Moldenke, and Coleothorpa Moldenke. The genus Megalostomis is the most diverse, with the largest number of species, distributed all along the range of the subtribe. This contribution includes a review on the biology, with updated information on host plants, association with ants, and natural enemies, documenting the complex biology of the megalostomines. In this thesis a comparative study of the external and internal adult morphology of Clytrini was undertaken. A new set of characters is described for the subtribe Megalostomina, from the internal sac of aedeagus, which provide useful phylogenetic signal. The ?mysterious? stridulatory organ of Neotropical clytrini is found to be located in the posterior margin of the head (vertex-pronotal), it is constituted by the pars stridens that rubber against a carina on the internal side of the prothorax (plectrum), this organ is described and illustrated for the first time, with a discussion of its phylogenetic value. Regarding morphology of the immature stages, a larval description of the tribe Clytrini is elaborated (along with phylogenetic implications of the larval characters for the higher phylogeny of these beetles), and original descriptions of the first instar larva of two species in two genera of Megalostomina are provided. More than 180 photographs illustrating the most important characters (74 characters and their respective states) used in the cladistic analysis are II Federico Alejandro Agrain provided. Based on these characters a total of 42 formal species are now recognized in the genus Megalostomis. A cladistic analysis of 57 terminal taxa and 96 characters was undertaken, under equal weights, and also using implied weights as a means to downweight homoplasious characters. The main objectives of the phylogenetic analyses were two-fold: at higher level, to test monophyly and explore intergeneric relationships of the subtribe Megalostomina, and regarding the genus Megalostomis (the study group), to reconstruct the relationships among the species, while testing monophyly of the genus and its constituent subgenera as in previous classifications. After cladistic analysis, it turns out that the subgenera of Megalostomis as in previous classifications are not natural units. The 42 species recognized in the material examined in this study can be assigned to two groups, one containing mostly species of North and Central america, and a larger one made up of mostly Southamerican species. However, they are not formally named as subgenera yet, being more prudent to wait until additional evidence supporting these clades become available for analysis, when performing the systematic revision of the remaining genera of Megalostomina. The systematic chapter contains diagnoses, descriptions or redescriptions, habitus photographs (dorsal and lateral) of all the species treated, a key to identify all of them, distribution maps and information on the Ecoregions that each species inhabit. In the descriptions, new characters of taxonomic importance, such as those coming from male and female genitalia, have been incorporated. A predictive distribution model, based on bioclimatic variables, was used to explore the potential distribution of the species of Megalostomis. The results provide additional support to the hypothesis that the species in this genus are adapted to arid environments, explaining their absence from the humid regions of South America as real, and not a result of lack of collecting. Nomenclatural changes proposed in this thesis are as follows. New taxa: Two species from Ecuador are described as new: Megalostomis huarmi sp. nov. and Megalostomis sergius sp. nov. Changes of status: Two subspecies changed their status to species: M. consimilis Achard 1926, stat. nov. as species (from subspecies of M. cornuta Lacordaire 1848) and M. dynamica Monrós 1952, stat. nov. as species (from subspecies of M. flavipennis Jacoby 1880). New synonymies: In accordance with the results of the cladistic analysis and the phylogenetic principles of monophyly, six of the formerly recognized subgenera of Megalostomis are synonymyzed under the latter genus Megalostomis (Megalostomis) Chevrolat 1837: M. (Minturnia) Lacordaire 1848, syn. nov.; M. (Heterostomis) Lacordaire 1848, syn. nov.; M. (Scaphigenia) Lacordaire 1848, syn. nov.; M. (Snellingia) Moldenke 1981, syn. nov.; M. (Coleobyersa) Moldenke 1981, syn. nov.; and M. (Pygidiocarina) Moldenke 1970, syn. nov. Thus, no subgenera are recognized within Megalostomis. The study of intra-specific variation and the new data of the geographical distribution range of some species resulted in several new synonymies (a total of 30) proposed within the genus Megalostomis: M. flavomaculata Lacordaire 1848, syn. nov. of M. flavocincta Lacordaire 1848; M. mariae Monrós III Systematics and Phylogeny of Megalostomina 1951a, syn. nov. of M. anachoreta Lacordaire 1848; M. metallica Jacoby 1888, syn. nov. of M. viridana Lacordaire 1848; M. affinis Jacoby 1888, syn. nov. of M. splendida Lacordaire 1848; M. propinqua Lacordaire 1848, syn. nov. of M. querula Lacordaire 1848; M. iracunda Lacordaire 1848, syn. nov. of M. luctuosa Lacordaire 1848; M. runa Monrós 1952, syn. nov. of M. basilaris Jacoby 1880; M. amazona Jacoby 1876, syn. nov. of M. anachoreta Lacordaire 1848; M. distincta Lacordaire 1848, syn. nov. of M. religiosa Lacordaire 1848; M. meretrix Lacordaire 1848, syn. nov. of M. gazella Lacordaire 1848; M. bicingulata Lacordaire 1848, syn. nov. of M. gazella Lacordaire 1848; M. tosta (Monrós 1950), syn. nov. of M. microcephala Lacordaire 1848; M. generosa Baly 1877a, syn. nov. of M. anachoreta Lacordaire 1848; M. bubalus Lacordaire 1848 , syn. nov. of M. tricincta (Germar 1824); M. hespenheidi Moldenke 1981, syn. nov. of M. anachoreta Lacordaire 1848; M. punctatissima (Jacoby 1888), syn. nov. of M. dimidiata (Lacordaire 1848); M. tomentosa Jacoby 1880, syn. nov. of M. dimidiata (Lacordaire) 1848. The following subspecies were synonymized with their senior species: M. bubalus bubaloides Monrós 1953a, syn. nov. of M. bubalus Lacordaire 1848; M. univittata oblita Monrós 1953a, syn. nov. of M. univittata Lacordaire 1848; M. univittata pacifica Monrós 1953a, syn. nov. of M. univittata Lacordaire 1848; M. splendida regalis Achard 1926, syn. nov. of M. splendida Lacordaire 1848; M. splendida affinis Jacoby 1888 , syn. nov. of M. splendida Lacordaire 1848; M. dimidiata picturata Achard 1926, syn. nov. of M. dimidiata Lacordaire 1848; M. dimidiata nayaritensis Moldenke 1970, syn. nov. of M. dimidiata Lacordaire 1848; M. dimidiata apicalis Achard 1926, syn. nov. of M. dimidiata Lacordaire 1848; M. dimidiata sonorensis Moldenke 1970, syn. nov. of M. dimidiata Lacordaire 1848; M. femorata australis Moldenke 1970, syn. nov. of M. femorata Jacoby 1888; M. fulvipes yucatanensis Moldenke 1970, syn. nov. of M. fulvipes Jacoby 1888; M. notabilis linearis Moldenke 1970, syn. nov. of M. notabilis Lacordaire 1848; M. subfasciata majorubrofasciata Moldenke 1970, syn. nov. of M. subfasciata (Leconte 1868); M. subfasciata murina (Monrós 1952), syn. nov. of M. subfasciata (Leconte 1868). Type designations: Lectotypes were designated on the basis of newly found Lacordaire`s syntypes from di Breme collection in Turin (Italy), for the species: Megalostomis gigas Lacordaire 1848, M. obesa Lacordaire 1848, M. cornuta Lacordaire 1848, M. religiosa Lacordaire 1848, M. dimidiata Lacordaire 1848, M. pyropiga Lacordaire 1848; lectotypes were designated on the basis of specimens in The Natural History Museum (London) for the species: M. placida Baly 1877b and M. interruptofasciata Baly 1877a; lectotypes were designated on the basis of specimens in the National Museum of Natural History (Smithsonian, Washington DC, USA) for the species: M. querula Lacordaire 1848, and M. tricincta Germar 1824. Furthermore, results of the cladistic analysis also support changes in the generic classification of the subtribe Megalostomina: Coleorozena Moldenke 1981, syn. nov. of Coscinoptera Lacordaire 1848; Coleothorpa Moldenke 1981, syn. nov. of Coscinoptera Lacordaire 1848; and Euryscopa (Coleoguerina) Moldenke1981, syn. nov. of Coscinoptera Lacordaire 1848. Other taxonomic changes suggested by the results of the cladistic analysis are delayed until a major taxon sampling and additional characters become available to analyze in further studies. Information provided by the agent in SIGEVA