Pyrgauchenia species

Stegmann, U. E., Webb, M. D. & Linsenmair, K. E., 2002, New species, synonymies and life-histories in the South-East Asian treehopper genus Pyrgauchenia Breddin (Auchenorrhyncha: Membracidae: Centrotinae), Journal of Natural History 36 (3), pp. 279-303 : 280

Life-histories of Pyrgauchenia species

There are few previous published accounts of Pyrgauchenia life-histories ( table 1). Melichar (1914) noted that in Java, E. Jacobson found adults and nymphs of P. foersteri together on a species of Melastoma (Melastomataceae) and on an unspeci- ®ed number of other plants, all tended by the ant Myrmicaria arachnoides Smith. Funkhouser (1935) reported that in Java, M. A. Lieftinck`frequently watched small colonies of ... [ P. recurva ] on the end-shoots of a small tree of Talauma candollei (L.)’ ( Magnoliaceae ). Observations were made throughout the year and the species was tended by Myrmicaria brunnea subcarinata Smith.

Field observations by the ®rst author show that host-plant species ranged from one to many per Pyrgauchenia species. Host-plants are de®ned, here, as those plants on which (i) Pyrgauchenia eggs together with nymphs or adults were found, or (ii) nymphs and adults were found. Two Pyrgauchenia species ( pendleburyi and tristaniopsis ) were clearly polyphagous, whereas two other species (? brevinota and colorata ) were found only on a single host-plant species ( tables 1, 2). To test if the apparent`monophagy’ in the latter two species was a sampling artifact (or not) we correlated (i) the number of host-plant species with searching eOEort and (ii) the number of host-plant species with host-plant individuals across the ®ve Pyrgauchenia species studied in the ®eld ( table 2). If a signi®cantly positive correlation is shown in either test, apparent monophagy in P. brevinota and P. colorata might be a result of low search eOEort and few plant individuals. Indeed, the number of host-plant species correlated positively with both searching eOEort (Spearman’s rank correlation coe - cient r 50.92, P <0.03, N 55) and number of host-plant individuals (Spearman’s r 50.92, P <0.03, N 55). Moreover, given that other treehopper species tend to have a similar degree of host-plant specialization within a genus (reviewed in Wood, 1993), and that two Pyrgauchenia spp. are polyphagous, it may be hypothesized that all species within this genus show some degree of polyphagy.

Ant partners were observed in all Pyrgauchenia species studied in the ®eld (see`Stegmann ®eld studies’ in tables 1 and 2 and species descriptions for details).The number of ant species as partners did not increase signi®cantly with searching eOEort (Spearman’s r 50.75, n.s., N 55). We cannot decide whether this ant speci®city is due to (i) low sample size, (ii) specialized symbiotic interactions or (iii) fewer potential ant partners due to decreasing ant biodiversity at higher elevations, as documented for Mt Kinabalu , Sabah, by BruÈhl et al. (1999) .

For the ®rst time we document maternal egg-guarding in Pyrgauchenia , a behaviour so far mostly associated with New World Membracidae ( Wood, 1993) . Eggguarding was found in all Pyrgauchenia species studied in the ®eld (see`Stegmann ®eld studies’ in table 1). In addition to the information in table 1 on maternal care for P.? brevinota , it should be mentioned that several aggregations of this species, with nymphs and adults, were found on one Wendlandia sp. plant at Sayap (Kinabalu Park, Sabah, 1000 m), with at least ®ve females sitting on egg clutches; aggregations were tended by two ant morpho-species, Myrmicaria sp. and Technomyrmex sp.