Fauna of New Zealand 72: Micropterigidae (Insecta: Lepidoptera) - Phylogeny
Gibbs, G W 2014. Fauna of New Zealand. 72, 127 pages.
(
ISSN 0111-5383 (print),
ISSN 1179-7193 (online)
;
no.
72.
ISBN 978-0-478-34759-3 (print),
ISBN 978-0-478-34760-9 (online)
).
Published 30 Jun 2014
ZooBank: http://zoobank.org/References/D6BC8C34-6D93-4EC7-BCB3-5670B2CFE744
DOI: 10.7931/J2/FNZ.72
Phylogeny
A molecular phylogenetic analysis of the family Micropterigidae was initiated by Y. Kobayashi and H. Suzuki at Tokyo Metropolitan University in 1997. Their analysis included five New Zealand taxa (four of Sabatinca + Zealandopterix) and used the ribosomal mitochondrial 16S gene. This ongoing project gradually incorporated samples from all continents (except India, where micropterigids were not known at the time (Lees et al. 2010.)), until it could be regarded as a worldwide phylogeny. At the time of writing, this molecular analysis has been extended to include nuclear rRNA genes 18S and 28S, but remains unpublished. A separate programme, with the goal of barcoding Micropterigidae of the World (MICOW) has been established in Barcode of Life Data Systems (BOLD) (Ratasingham & Hebert 2007). It is more comprehensive, with the New Zealand component incorporating multiple examplars of all the New Zealand taxa in a survey covering about 170 taxa world-wide. Analysis of this database forms the basis of the following discussion (see Gibbs & Lees 2014 for methodology and accessibility of data; and simplified cladogram p. 24).
The most significant finding on a world scale, is the retrieval of five major clades in the family Micropterigidae, two northern hemisphere, three southern. The five clades are unambiguously defined in all analyses and appear monophyletic, but their inter-relationship topology cannot be supported with a high degree confidence. This topology, and even evidence of a primary southern-northern hemisphere dichotomy within the family, remains to be tested with additional molecular markers. Reassuringly, a number of morphological traits can be correlated with the five world clades (Hashimoto 2006). Here, the phylogenetic relationships and biogeographic interpretation of New Zealand species are discussed, based on the molecular analysis presented in Gibbs & Lees (2014).
As well as its contribution to taxonomic species grouping, bar-code analysis has identified larval morphs, confirmed the three synonomies proposed in this revision from morphological data, and also confirmed the identity of pairs of sister species (discussed within the relevant species descriptions and in relation to biogeography). The identification of three subclades within Sabatinca on the main islands of New Zealand has important implications for biogeographic inference, particularly with regard to the occurrence of Sabatinca in New Caledonia.
Congruence between morphology and phylogeny
This study has revealed a degree of heterogeniety within New Zealand Sabatinca that warrants subdivision into species groups, definable from either morphological or molecular characters. The use of these two independent character sets for analysing species diversity enables an evaluation of the strength of phylogenetic signals contained in the basic morphological structures that we use for alpha-taxonomy. Some selected genital characters are reviewed below with a view to noting features that carry a reliable phylogenetic signal as opposed to those which have taxonomic value only. ‘Reliable’ is defined as a phylogenetic signal that is supported by both the morphological and molecular character sets.
This review has confirmed an extant New Zealand fauna of 18 species in the genus Sabatinca. There is no evidence (with the possible exception of the aemula/chrysargyra species pair (see above)) of sibling species complexes that might illustrate a burst of recent divergence (i.e., evolved within the last 5 Ma). It is thus not surprising to find that the New Zealand species are stable, well-defined entities, easily recognisable from a glance at a colour image, and moreover, that their genital morphology, especially the male, provides unambiguous confirmation of identity. Interestingly, the situation is entirely different in New Caledonia where a number of species complexes have been revealed within the Sabatinca fauna.
Male genitalia: Phylogenetic analysis indicates that development of a massive vinculum (segment 9 sclerite), which seems so characteristic of members of the genus Sabatinca, is clearly a widespread groundplan feature. An elongated vinculum can appear in four of the five world lineages of Micropterigidae, although often in only one or two species. It is absent from the remarkably consistent Northern Hemisphere Micropterix clade. The robust vinculum is best interpreted as a structure of major functional significance but with little phylogenetic signal. By way of contrast, the micropterigid phallus is found to reveal more phylogenetic information than any other part of the genital complex. Some traits are significant at the lineage level, others at genus or species level. Those with lineage significance are described below:
Relative length of the phallobase: In three of the five lineages of Micropterigidae, the phallobase is considerably longer than the distal phallus (e.g., in the Zealandian Sabatinca lineage, the ratio of phallobase: overall phallus is in the range 0.6–0.9. However, in the Australian lineage (e.g., Tasmantrix) this relationship is reversed (ratio 0.3–0.4) and in the Asian-North American lineage (e.g., Neomicropterix) it can be close to equal (0.5–0.6).
Bulbus ejaculatorius aperture: The anterior termination of the cuticular phallobase tube is clearly defined in genitalic preparations and seems to be relatively consistent in the limited number of comparative specimens available for this study. The plane of the terminal phallobase aperture is essentially at right angles to the longitudinal axis in the Micropterix lineage of Europe. In the Asian lineage the phallobase tube is bent at its anterior end to bring the aperture into a longitudinal ventral orientation, parallel with the axis of the phallus. The anterior aperture is oblique in the remaining three lineages.
Gonopore details: In the hypothetical groundplan micropterigid, the gonopore is probably an open, more-or-less circular aperture which can be either terminal or toward the dorsal side of the phallus. In a few cases, notably the genus Tasmantrix and its allies in the Australian lineage, there is a dorsal component which overhangs the gonopore like the upper part of a vertebrate jaw. A series of close-set, sclerotised radial folds which surround the margin of the gonopore are a probable micropterigid autapomorphy (Kristensen 1984b), but in the two northern hemisphere lineages there is an additional blind ventral branch of the distal phallus extending beyond the gonopore. This ventral branch seems universally present in Micropterix species but has only been reported from Epimartyria in the Asian-North American lineage (Hashimoto 2006). In each of the three southern hemisphere lineages there are numerous examples of an expanded ‘ventral bulb’ developed below the gonopore but no discrete ventral branch as in Micropterix and Epimartyria. The morphological and phylogenetic significance of these features have not yet been investigated. It goes without saying that the remarkable degree of gonopore diversity can be valuable for species-level determinations.
Characters of the phallus are illustrated and cited extensively in this revision for all taxonomic levels.
Female genitalia: The presence of large tri-radiate signa in the corpus bursae of certain micropterigids invites taxonomic analysis but appears to offer little of phylogenetic value. Four signa occur consistently in members of the calliarcha group and the New Zealand incongruella group of the Sabatinca lineage. Four remarkably similar signa also occur in certain taxa of the Asian/N American lineage. An intriguing correlation between the existence of signa and the presence of a sclerotised ‘pleural pocket’ modification of segment 8 (see discussion p.14) is found only in the Sabatinca lineage and is extensively developed in many New Caledonian species (where females in 27 out of 41 species examined had this feature in conjunction with the development of signa). It has been suggested that large signa are likely to be associated with the breaking up of spermatophores and indeed dissections of Sabatinca specimens have sometimes found fragments of spent spermatophores remaining within the corpus in these cases (Gibbs & Lees 2014). A dissected female specimen of Epimartyria (North America) also contained spermatophore fragments in conjunction with large trident signa (unpublished observation).
In contrast to the signa discussed above, an examination of spermathecal morphology will repay the time needed to make suitable preparations of these delicate structures:
Spermatheca: Although relatively consistent throughout many lepidopteran groups, the degree of spermathecal differentiation in the New Zealand Micropterigidae is significant and offers valuable phylogenetic insight. While ductus and lagena remain relatively constant throughout the family, the utriculus varies from the most basic simple form in Zealandopterix (Fig. 209—a single elongate thin-walled chamber), to the complex utricular differentiation of certain Sabatinca species, where up to four distinct regions can be distinguished. Of particular interest is the strong correlation with the phylogenetic relationships established by barcoding analysis. For instance, the utricular modifications shown in Fig. 229–235 and Fig. 238–241, spanning the aurella-subgroup and chalcophanes-subgroup respectively, clearly indicate patterns that support subdivision into two basic forms within the chrysargyra-group clade. Quite different modifications characterise the incongruella- and calliarcha-group clades. In particular, the presence of a discrete spherical loculate organ at the junction between utriculus and lagena (Fig. 221–226). This spherical organ is a feature of the New Caledonian Sabatinca fauna as well as these two New Zealand clades.