FNZ 17 - Mymaridae (Insecta: Hymenoptera) - Faunal Relationships
Noyes, JS; Valentine, EW 1989. Mymaridae (Insecta: Hymenoptera). Fauna of New Zealand 17, 100 pages.
(
ISSN 0111-5383 (print),
;
no.
17.
ISBN 0-477-02542-0 (print),
).
Published 28 Apr 1989
ZooBank: http://zoobank.org/References/1D0A405D-6643-42DB-B911-80664BC6F853
Faunal Relationships
The mymarid fauna of New Zealand (including the offshore islands from the Kermadecs to Campbell Island; see inside front cover) is particularly species-rich. It is known to comprise at least 160 species, many of which are undescribed, in 42 genera. This is a very high number when compared with similar land-masses in other areas. For example, the British mymarid fauna, one of the most extensively studied in the world, comprises only 84 species in 16 genera (Fitton et al. 1978), which is approximately half as many species per unit area as occur in New Zealand. The size of the New Zealand mymarid fauna is even more remarkable when one considers that it is approximately equivalent to 10% of the described world species. Within New Zealand the species richness of mymarids in relation to other chalcidoids is also unusually high; about 25% of the total number of chalcidoid species are mymarids, which compares with an average of less than 10% for the rest of the world.
The proportion of flightless species or species that have some flightless individuals is also exceptionally high, there being at least 17 genera in New Zealand that include species with abbreviated wings. This is probably a result of being associated with habitats where flight is not advantageous, or where wings may be an encumbrance when searching in dense habitats, e.g., alpine grasslands, leaf litter, or moss. The largest number of species with flightless individuals are associated with leaf litter.
Table 1 summarises the zoogeographic relationships, at a generic level, of the New Zealand mymarid fauna. It can be seen that most genera (20) appear to be endemic, and cosmopolitan genera make up most of the remainder (13). Four genera are found only in Australia and New Zealand and a further three genera are more widely distributed, being found also on the Indian subcontinent.
The patterns of distribution of the genera not belonging to the Australomymar-group are difficult to comment upon because they belong to groups of cosmopolitan distribution. Cosmopolitan genera (or species-groups) are, in the main, poorly defined, and in many instances their status is controversial (see Huber 1986), particularly those related to Polynema. For instance it is possible that Richteria, a genus apparently confined to Australia and New Zealand, will be considered a polyphyletic assemblage of species belonging to the cosmopolitan genus Polynema. The species here placed in Dicopomorpha may be placed similarly in the cosmopolitan genus Dicopus, or all species of Prionaphes may be placed in the cosmopolitan genus Cleruchus. Until the classification and phylogenetics of the Mymaridae are studied on a world-wide basis, any comment concerning the zoogeographic relationships of these groups must be speculative.
The distribution of Australomymar, a genus restricted to New Zealand, Australasia, and South America, warrants some discussion since its nearest relatives (see Australomymar-group) are limited to New Zealand and Australia. This genus may represent a relict group of relatively primitive genera of earlier southem distribution, but there is no fossil evidence to support this view. Very few fossil mymarids are known, the oldest being about40 million years old (see Yoshimoto 1975), whereas any possible land connection between Australia and South America probably ceased at least about 55M years ago, and between Australia and New Zealand at least about 80M years ago (Rich 1975). However, it is possible for insects to cross the Tasman Sea even today (Fox 1978). In support of the view that Australomymar represents a relict group of southerly distribution is the fact that, of the known extant genera, this genus is possibly one of the closest to the hypothetical primitive mymarid. It is likely that the most primitive mymarid would have had a forewing with long marginal and postmarginal veins, five-segmented tarsi, and a thirteen-segmented antenna. In no known extant mymarid genus is this the case, although a genus recently collected in Western Australia has all these attributes except that the antenna of the female is twelve-segmented (BMNH, CNCI). Australomymar has a long marginal vein on the forewing, and in some species the postmarginal vein is long. However, the tarsi are four-segmented and only the antenna of the male has thirteen segments, the female antenna being nine-segmented. Cosmopolitan genera showing several of these primitive states are Gonatocerus and Arescon, but neither of these has a postmarginal vein apparent. In addition the forewing venation of Gonatocerus is generally very short and the female antenna is eleven-segmented, and the female antenna of Arescon is only eight-segmented. To date there is no phylogenetic evidence to suggest that the Australomymar-group, as defined here, is closely related to Arescon or to Gonatocerus. The Australomymar-group (see page 8) comprises 12 of the 42 genera and 56 of the 163 species of mymarids known from New Zealand. This indicates that it is particularly species-rich here, as well as morphologically diverse. By way of comparison, in Australasia the group is represented by only 5 genera and not more than 25 species. In South America it is represented by a single genus containing not more four or five species (all undescribed; CNCI, BMNH).
Not belonging to the Australomymar-group, but perhaps also a relict of an earlier southern distribution, is the genus Anagroidea. This does not show any of the primitive characters outlined above, but it is only one of perhaps two or three genera of mymarids (the others placed in the subfamily Eubroncinae - not yet found in New Zealand) in which the wing membrane extends to the base of the hindwing. This might be the primitive state of the hindwing, with a petiolate hindwing the more derived condition (see Gibson 1986).