FNZ 62 - Trechini (Insecta: Coleoptera: Carabidae: Trechinae) - Higher classification
Townsend, JI 2010. Trechini (Insecta: Coleoptera: Carabidae: Trechinae). Fauna of New Zealand 62, 101 pages.
(
ISSN 0111-5383 (print),
ISSN 1179-7193 (online)
;
no.
62.
ISBN 978-0-478-34717-9 (print),
ISBN 978-0-478-34716-6 (online)
).
Published 16 Jun 2010
ZooBank: http://zoobank.org/References/0D2B064C-C2E0-41F8-AB9A-BEB2E4B41412
Higher classification — historical background
In the 1970s and 1980s ideas on the world classification of Trechini appeared to be settling in favour of those proposed many years earlier by Jeannel. Provided his nomenclature was reduced in rank (his subfamilies became tribes and his tribes became subtribes) his overall plan remained largely intact.
For a time, the 5 “tribes” Jeannel (1926, 1927, 1928) established (Perileptini, Trechodini, Trechini, Aepini, Homaloderini) were rearranged, combined, or expanded as various characters were given emphasis in the belief that they were of greater or lesser phylogenetic significance. Laneyrie (1974) pointed out many of the shortcomings of previous attempts at an overall classification of the Trechini (or “Trechidae” — he considered them to be of even higher taxonomic rank than Jeannel), but did not provide a solution to the problems. He stated, and the New Zealand fauna seems to confirm, “that while regional faunae can be placed in what appears to be a reasonable taxonomic system, the combination of these systems on a world basis causes the greatest difficulty.” It would be presumptuous of me to attempt such an overview, and the following is intended only to give an indication of how the broader systematics can be seen from the viewpoint of a detailed study of the New Zealand fauna.
A world classification and checklist by Casale & Laneyrie (1982) divided the family into 2 subfamilies, the Trechodinae and the Trechinae, on the basis of the aedeagus being open dorsally and gutter-like in the former group. Within the Trechodini, the authors placed the Cnidini, Trechodini, and Plocamotrechini. In the Trechinae they placed the Perileptini, Aepini, and Trechini (within which they included the Homaloderini). The Perileptini were separated on account of their pubescent eyes and the penultimate labial palpomere having more than 4 setae. This placement of the Perileptini, however, is not supported by other internal structures, including those of the important male genitalia (Uéno 1989). The shape of the male genital segment also links the Perileptini and Trechodini, which cuts across their 2 subfamilies. The character of pubescent eyes is not clear-cut in some species.
Casale & Laneyrie (1982) separated the Aepini from the Trechini by their small size, being apterous and depigmented with very small eyes, having a premolar tooth, and the anterior tibiae having a spur on their external face. All the rest they grouped in the Trechini, as not having the above characters. This does not work well for some of the New Zealand species.
Moore (1972) revised the trechine fauna of Australia and Tasmania, but did not divide the group below the Trechini, arguing that there was no clear-cut difference between the homaloderine and trechine lineages of the tribe.
Bousquet & Larochelle (1993) in their catalogue of North American carabid fauna retained the 6 tribes of Casale & Laneyrie (1982), but reduced them all to subtribes, i.e., Cnidina, Trechodina, Plocamotrechina, Perileptina, Aepina, and Trechina, in which they included the Homaloderina (under the name Aemaloderina). The fauna of America north of Mexico all belonged to their expanded subtribe, Trechina. This followed Moore’s treatment of the Australian fauna, the argument as to whether they were Trechina or Homaloderina not arising.
Klimaszewski & Watt (1997) included the Bembidiini in the subfamily (as is generally recognised now) and included an illustration of Zecillenus alacris (Broun) as an example of the Trechinae. Lawrence, in an appendix to this work, defined the Trechini and it is this group, as defined by Lawrence, that is the subject of this revision.
In their catalogue of the New Zealand Carabidae Larochelle & Larivière (2001) followed the classification of Moore (1972). However, the Australian fauna, apart from the very distinctive Trechodini, consists entirely of the homaloderine lineage, whereas in New Zealand there are clear examples of homaloderine, aepine, and trechine lineages.
Larochelle & Larivière (2007) published a synopsis of superaspecific taxa of New Zealand Carabidae, including the Trechini. They divided the New Zealand genera of the tribe into 2 subtribes, the Aepina and the Trechina. but did not recognise the Homaloderina as distinct. They also described 2 new genera of trechines in this work, which I consider unfortunate in that Larochelle was aware of my ongoing work to revise the Trechini. Drs Uéno and Giachino had recognised these new genera some years ago, but generously refrained from describing them to leave them for characterising in this revision in context with all Trechini taxa.
New Zealand perspective
This study has been ongoing for some years, during which time various world and regional revisions and new discoveries here in New Zealand have been made. For the most part, the New Zealand fauna seems to fall conveniently into the classical arrangement of tribes (or subtribes), except for a few problem species. Therefore, my initial thoughts followed the basic arrangement of Jeannel except for some minor modifications. For instance, in New Zealand there is a well-defined group of trechines that I regard as homaloderine, in spite of the fact that they are all blind, cavernicolous forms, a characteristic apparently not known for this subtribe in South America, where it forms a major part of the fauna. This same group of cavernicolous forms can be recognised in the Australian and Tasmanian faunas but has been classified there as Trechini by Moore (1972) as he considered the tribes Trechini and Homaloderini to be synonymous. Subsequently, Moore, in his catalogue of the Australian Carabidae (Moore et al. 1987) placed them all in the supertribe “Trechitae”, which also included genera usually placed in the tribes Zolini, Bembidiini, and Pogonini, and did not subdivide them further. However the New Zealand fauna contains true Trechini sensu Jeannel (apparently absent from Australia) and here at least, the old tribes or subtribes “Trechina” and the “Homaloderina” can be separated quite satisfactorily as distinct lineages by the shape of the female genitalia, and other characters including those of the mouthparts.
Examination of female genitalia shows major differences between the New Zealand examples of the Aepine lineage and the Homaloderine lineage, with the enigmatic genus Neanops (and others) falling into the former, although it is a cave dweller with greatly reduced eyes. Previously, aepines have been recognised by their association with the sub-littoral habitat. Within our Aepine lineage, the possession of a well-defined external tibial spur as in Kenodactylus, is modified into a thicker spine among other bristles in Maoritrechus, and although Oarotrechus must be classed as belonging to the same lineage, based on its general morphology and the fact that it lives in marine gravels, it does not have an external spur but instead this is replaced by a series of dense bristles. Neanops caecus also has similar dense bristles and no spur, but N. pritchardi does have a small spur. So the presence of the tibial spur does not provide a clear-cut demarcation for the New Zealand fauna. However, the structure of the female genitalia puts Neanops clearly in the Aepine lineage in spite of it being a non-marine cave inhabitant. The arrangement of the female genital tract is of great importance when considering the higher classification of the Trechini and many other groups of Carabidae and its significance cannot be ignored.
In 1999 another cave-frequenting aepine was found in Northland (the first troglobitic carabid from the region) which has confirmed for me that the Aepine lineage does include cave-dwelling species. Unfortunately the only known specimen of this fascinating species is a slightly teneral male, so what the female genitalia look like remains unknown at this time. This Northland species does have the typical aepine spur on the outer side of the fore tibiae, but it also has elytra that are not truncate and has sharp pointed homaloderine mandibles. So almost all the external characters for separation have broken down. This could be an argument for abandoning the separate lineages; however, a female would be expected to have aepine type genitalia. It appears that a group of aepines in New Zealand have adapted from the sub-littoral to the subterranean environment.
In this interpretation, the New Zealand fauna does not contain any examples of the Perileptini or Trechodini lineages that have been recognised in other parts of the world, but has representatives of what have been previously thought of as Aepina, Homaloderina, and Trechina, now perhaps better thought of as distinctive lineages within an expanded Trechina rather than formal subtribes. I have also been guided particularly by the shape of the male genital segment (9th sternite), a character that to my knowledge has not been used in trechine classification before. As this is an internal structure, unlikely to be modified by secondary environmental adaptions, its shape may well be of phylogenetic value. An examination of rather limited overseas material showed the shape of this structure supports Jeannel’s earlier classifications (including 1941), but refutes his later (1960) idea of placing the Perileptina near the Trechina. It shows the Perileptina and the Trechodina to be closely related and quite distinct from the rest of the tribe (Figs 153–165).
A study of larval morphology has not been included in this revision because there are very few examples available. Among those that are available are Kenodactylus and Maoritrechus which have double claws (Johns 1974) and Duvaliomimus (Mayotrechus) mayae which has single claws (May 1963). The significance of this would require more study. However, Grebennikov & Maddison (2005) after a study of world-wide trechine larvae have come to the conclusion that the Perileptina are related to the Trechodina as suggested by Uéno (1989), and further supported by the shape of the male genital segment. Grebennikov & Maddison (2005) showed the Trechini as a whole to be of monophyletic origin, whereas the Bembidiini are probably polyphyletic.