Análisis histórico de la clasificación de los coleoptera Scarabaeoidea o Lamellicornia

Abstract

Se presenta una revisión histórica del proceso de clasificación y el desarrollo de la sistemática de los Lamellicornia o Scarabaeoidea (Insecta: Coleoptera), dividida en tres períodos. El análisis comprende un estudio histórico-comparativo sobre el desarrollo del tipo y número de caracteres, así como el número y características de los géneros y agrupamientos en taxones supragenéricos. El primer período abarca 14 autores en diferentes fechas, iniciando en 1735 con Linné y terminando en 1856 con Lacordaire. En este período se abordan trabajos anteriores a la publicación del "Origen de las Especies", por lo cual las ideas evolucionistas darwinianas no tuvieron influencia sobre la sistemática del grupo. En el segundo período se presenta una comparación de las propuestas de clasificación de los Coleoptera Scarabaeoidea, publicadas entre 1869 y 1955 por 17 autores de trabajos faunísticos y taxonómicos regionales o en catálogos mundiales. Se destacan los principales caracteres morfológicos utilizados para la separación supragenérica y las inovaciones introducidas por cada uno de ellos, señalando en su caso, la posible influencia de las teorías de Darwin. Se concluye que el esquema general de clasificación durante este período no cambió substancialmente con respecto al de Burmeister o Lacordaire, y que las ideas evolucionistas tuvieron poca repercusión en estas clasificaciones, las cuales son más complejas que las del primer período, sobre todo por la adición de más de 11,000 especies nuevas obtenidas durante 80 años de exploraciones mundiales. En el tercer período se resumen y analizan las propuestas de clasificación publicadas entre 1957 y 2001 por 28 autores de monografías, estudios faunísticos y claves regionales, artículos sobre morfología comparativa, y trabajos expresamente enfocados al esclarecimiento de las relaciones filéticas y los procesos evolutivos de los Scarabaeoidea en conjunto, o por grupos supragenéricos particulares de esta superfamilia. En la mayor parte de estos estudios es evidente la influencia de las teorías sobre la evolución orgánica, y se observa como progresivamente se busca que las clasificaciones reflejen las relaciones entre sus elementos, principalmente a través de enfoques feneticistas y cladistas.

Translated abstract

This study presents an historic analysis of the classification process of the Scarabaeoidea (Insecta: Coleoptera). The analysis is divided in three periods including 59 authors, beginning with Linné in 1735, and finishing in 2001 with Pretorius and Scholtz. The first period (1735-1856) was chosen, since it encompasses a time period prior to the publication of Darwin's "The Origin of Species", and is therefore a classification process arguably free of any Darwinian evolutionary influences. There was a very quick development, in a relatively short period of time (1735-1796), in the number and type of characters used for classification purposes. On some occasions, certain authors reverted to the pre-Linnean tradition of using ecological characters. Likewise, the hierarchic structure of classifications developed rapidly into systems that any modern taxonomist can relate to. Authors like Linné, Fabricius and Latreille, who worked for long periods of time developing classificatory systems, always revolutionized systematics in their very first study. Later on, they remained conservative and made improvements only to the details of systematics. By 1856, the classification of the scarab beetles looks very akin to any present-day system. It is obvious that classifications similar to modern ones can be approximated without having to rely on Darwinian evolutionary principles. The second period (1869-1955) includes a comparative synthesis on the classification of the Coleoptera Lamellicornia based on faunistic and taxonomic works dealing with species from Central America, Europe, India and Indochina, as well as classic world wide checklists, that are representatives of the taxonomical criteria of 17 authors; the possible influence of Darwin's theories is discussed for each classification. Apparently, the main structure of the classification of scarab beetles during this time does not show substantial changes in relation with the proposals of Burmeister or Lacordaire. A large number of new morphological characters were added to the traditional ones, but the family level characters and their use were nearly the same as in the middle of the XIX century. Male genital capsules, internal organs and structures of the immature stages were cited for the first time as useful taxonomic characters, but as accesories of the traditional adult characters. Relations between the groups were eventually exposed as dendrogrames by Sharp and Muir (1912), Paulian (1948) and Crowson (1955), but without clear references to evolutionary theories. These classifications were more complex than the preceding ones, because of the addition of nearly 11,000 new species discovered along 80 years of world exploration. The third period (1957-2001) resumes and analyzes the classification proposals undertaken by 28 authors, based on monographs, faunal studies, keys for regional fauna, papers on comparative morphology, and studies specifically devoted to the understanding of phyletic relationships and evolutionary processes in Scarabaeoidea, for the whole group or for suprageneric groupings of this superfamily. One can detect the patent influence of organic evolution theories on these studies, as well as a progressive reflection of relationships in the proposed classifications, mainly through the use of cladistic and pheneticist approaches. Lately, molecular approaches have also been recruited; but even with all this technology, the main problem remains that most studies do not consider all the diversity of the Scarabaeoidea in one single analysis. Mention must be made of Endrödi's study (1966), who is the first to consider the whole group in analytic and comparative style, proposing to subdivide the Lamellicornia into five families: Scarabaeidae, Melolonthidae, Trogidae, Passalidae and Lucanidae. This proposal has been supported by Martínez (1970-1990), Machatschke (1972-1974), and Morón (1976-2002). So far, no one has refuted this proposal by doing an equivalent or more modern analysis of his grouping. Medvedev (1976) and Iablokoff-Khnzorian (1977) have also made comparative studies, which, like Endrödi's proposal, have not been accepted by English speaking authors. Paulian's (1948-1988) and Balthasar's (1963) proposals were based mainly on the action of elevating subfamilies to the family status, so they do not really represent a new proposal. Using different points of view Lawrence and Newton (1982, 1995) and Scholtz (1990-1995) have supported Crowson's (1955-1981) proposals of 6-10 families of Scarabaeoidea. Historical, economic and sociopolitical factors have been influencing the development of the schools of systematics during the XX century. American authors have supported most of the time classificatory schemes that go against dividing the Scarabaeoidea, although lately they have started to adopt the 12 families scheme of Lawrence and Newton. On the other hand, European authors have tended to favor groupings with as many as 25 families, as proposed by Paulian and Balthasar. Although the studies undertaken by the South African school show a stronger methodological basis, the proposal of 15 families has not been accepted by Lawrence and Newton, although they have incorporated a great part of its structure. This last proposal shows still several problems to be solved in the family that includes the Scarabaeinae, Aphodiinae, Melolonthinae, Dynastinae, Rutelinae, and Cetoniinae; but it is shown by Jameson and Ratcliffe (2002) as the contemporary option to frame the study of the Scarabaeoidea.