Coenagrionidae) Phytotelmata, Pools Epiphytic Plants

Odonalologica 16(2): 193-199 June I, 1987 Seasonality, abundance and invertebrate associates of Leptagrionsiqueirai Santos in Aechmea bromeliads in Venezuelan rain forest (Zygoptera: Coenagrionidae) L.P. Lounibos¹,J.H. Frank²,C.E. Machado-Allison³, J.C. Navarro³ and P. Ocanto³ 1 Florida Medical Entomology Laboratory, University of Florida, 200 9th St SE, Vero Beach, Florida 32962, United States department of Entomology and Nematology, University of Florida, Gainesville, Florida 32611, United States 3 Institute de Zoologia Tropical, Universidad Central de Venezuela, Apartado 47058, Caracas 1041, Venezuela Received October 28, 1986 / Accepted December 11, 1986 In lowland tropical rainforest in eastern Venezuela the aquatic invertebrate fauna A. A. ml of 160 nudicaulis and 157 aquilega of 50-100 fluid capacity was inventoried. Larvae L. in has central tank of siqueirai occurred 35,3% ofA. aquilega which a small and axils in of many but only 11.0% A. nudicaulis which possesses a larger central tank but fewer axils. The incidence of larvae was significantly higher in the dry in wet to 7 L. larvae (29.4%) than the (16.6%) season. Up siqueirai were recorded from individual A. aquilega, and the frequency distribution of larvae in this bromeliad sp. fits a negative binomial. The most abundant invertebrates in Aechmea were Diptera (Culicidae, Thaumaleidae, Chironomidae, Ceratopogonidae,Psychodidae, and Reductions abun- Tipulidae), Coleoptera (Helodidae), oligochaete worms. in dance these due among any of taxa to predation by L siqueirai could not be demonstrated. However, the predaceous mosquito Toxorhynchiles haemurrhoidalis was negatively associated with and suffered reduced survivorship in the presence ofL. siqueirai, probably due to predation by the latter. INTRODUCTION of held terrestrial Phytotelmata, pools water by or epiphytic plants, are significant habitats for tropical Zygoptera. CORBET (1983) recorded 36 species from ten genera ofZygoptera believed to be relatively specific for phytotelmata. These 194 L.P. Lounibos et al. include eight of the species neotropical genus Leptagrion identified from terrestrial and bromeliads in Brazil epiphytic (SANTOS, 1966, 1968a, 1968b 1978 1979). In the of course experiments on a predatory mosquito larva, Toxorhynchites haemorrhoidalis in (Fabr.), Venezuelan phytotelmata, we discovered the relatively common occurrence of damselfly larvae in epiphytic bromeliads. On the basis of one adult female and adult male one reared from these larvae, thespecies was identified Professor A.B.M. Machado by as Leptagrion siqueirai Santos. The remaining collected larvae were assumed to be L. siqueirai on the basis of a common phenotype, but identifications adults positive on were not made. Else- where in Venezuela Leptagrion fernandezianum Racenis has been reported from Aechmeabromeliads (DE MARMELS, 1985); however larvae of this species do not bear a thoracic mark which conspicuous yellow we observed on all specimens assumed to be L. Prior siqueirai. to our collections, only malesofL. siqueirai had been known, these from being Pernambuco state in Brazil (SANTOS, 1968b). Quantitative information from our collections is reported here as a contribution to the information scanty about the life history of Leptagrion in bromeliads. STUDY SITE AND SAMPLING METHODS Collections were made on a cacao in lowland plantation tropical rain forest near Panaquire, Venezuela (10° 13' N, 66° 14' W) in the wet season and of and (July August) 1983 dry season(March and of 1984. April) The mean annual rainfall at Panaquire is approximately 2,500 mm, and fluctuates more than few from the annual temperature rarely a degrees mean of 26.3° C (MACHA- DO-ALLISON et al., is the rainiest and March 1983). July usually the driest month of the year. records Although for 1983-84 were not available from El Panaquire,at Cafe, 15 km to theSW, 46% less rainfall was registered during July 1983 than the 1961-70 of In mean 262.8 mm. March 1984, of the of 43.2 rainfall only 15% ten-year average mm was recorded at El Cafe. Shade and cacao the trees at plantation support five species of bromeliads which maintain phytotelmata (MACHADO-ALL1SON et al 1985). For experiments reported in detail elsewhere et in selected four (LOUNIBOS al., press), we phytotelmata, including two species of Aechmea which differ in structure. Aechmea nudicaulis (L.) possesses a prominent central tank and relatively few axils and Aechmea aquilega (Salisb.) has a reduced tank and axils many (MACHADO- -ALL1SON et Bromeliads 1 al., 1985). holding 50-100 ml of fluid were cut at levels to 10 m above from ground trees and in in the shade rack above suspended pairs on a 1.5 m groundfor oneto three months to allow Bromeliads natural colonization after rainfall. were not washed before suspension on the rack. first-instar larvae of T. haemorrhoidalis Single were released into the central tanks of 40 A. aquilega and 40 A. nudicaulis once duringthe and onceduringthe wet dry season; paired controlsreceived no introductions. the One-half of bromeliads weresampled 10 d after, and the remainder 20 d after the introduction. Bromeliads removed from the bucket were rack, shaken vigorously in a ofwater to dislodge inhabitant fauna, washed with a stream of water, and the contents of the bucket passed through a sieve of micron mesh later 160 width. Specimens were separatedfrom detritus in ethanol and preserved in formalin. All aquatic invertebrates visible with the naked eye were counted and identified. Similar methods have been used to censusthe invertebrate fauna of Tillandsia bromeliads in Florida'(FRANK, et al.,.1976). Leplagrion siqueirai in Aechmea bromeliads 195 RESULTS SEASONALITY AND ABUNDANCE Larvae recovered from of Aechmea in were 16.6% sampled the wet season of 1983 and from of inventoried in the of 29.4% plants dry season 1984(Fig. 1). A G-test confirmedthat the occurrence ofL. siqueirai in Aechmea was not indepen- of = dent season (G adj 141.8, P « 0.001). These same data revealed the presence of L. siqueirai in 11.3% of all A. nudicaulis and 35.0% of A. aquilega, indicating a significant habitat preference for the latter bromeliad species (G adj = 160.5, P« 0.001). Although L. siqueirai occurred most often as single individuals in plants, a maximum of five larvae was recorded from a single A. nudicaulis and a maximum of seven from a single A. aquilega (Fig. 2). The frequency distribution of numbers in A. aquilega deviated significantly from a random (Poisson) distribution (chi-squared = 18.49, P < 2 binomial 0.001, df), but a negative calculated by the iterative method of BLISS & FISHER (1953) provided an = acceptable fit to the data (chi-squared 5.73, P < 0.05, 2 df). The small value ofK. Fig. I. The incidence of L. siqueirai larvae = 0.895 indicates aggregation of L. in experimental bromeliads. Sample sizes siqueirai in A. aquilega. for are 80 plants each bar except wet- -season A. aquilega for which n = 77. RELATIONSHIPS TO OTHER INVERTEBRATES identified Most invertebrates were only to family. Eight taxa which include families of insects ofannelids for of seven and one class accounted 97.4% 11,050 organisms identified from experimental A. aquilega and 95.0% of 5,656 specimens from experimental A. nudicaulis. A. complete listing ofall identificationsis presented elsewhere (LOUNIBOS et al, in press). Leptagrion siqueirai accounted for only 0.8% and 0.4% of invertebrates identified from A. aquilega and A. nudicaulis, respectively. The median and maximum values of number of individuals of the eight 196 L.P. Lounibos et al. commonest taxa are given in Table I for Aechmeawith and without L. siqueirai which contained no T. haemorrhoidalis. In A. nudicaulis, no significant differences were detected within taxa in the presence versus absence of L. siqueirai. However, in A. aquilega, Culicidae, Thaumaleidae, Chironomidae, Tipulidae, and Helodidae were significantly more abundant in plants containing L. siqueirai. Elsewhere, we demonstrated that survival of Fig. 2. The frequency distributions of numbers of L. siqueirai larvae per plant in 157 experimental A. aquilega introduced T haemorrhoi- and 160/1. nudicaulis. dalis was significantly (P = 0.06) less in experimental bromeliadswhich containedL. siqueirai thanin plants which had no L. siqueirai larvae. Evidence of predation was also supported by a 2 X 2 contingency table analysis of pooled data from A. aquilega and A. nudicaulis, which indicated Table I numbers and of the abundant invertebrates in the Median ranges (parentheses) 1 most presence and absence of L siqueirai in Aechmea bromeliads which contained no Toxorhynchites No. 2 Helodidac Culicidae Thaumakidae OOligochaeta11 Helodidac Culicidae Thaumaleidae ChironomidaeChironomidac Ccratopogonidae PsychodidaePsychodidae Tipulidae plants A. nudicaulis:nudicaulis: Lepiagrion 14 7 I133 1I 1.5 0 3.5 1I present (46) (23) (12) (22) (14) (13) (77) (5) ns’ns} ns ns ns ns ns ns ns Lepiagrion 83 2 1I 2 0 I1 0 9 1 absent (62) (49) (41) (19) (15)(15) (22) (74) (17) A.aquilega:aquilega: LeptagrionLepiagrion 45 0 0 10 0 99 I1 28 2 present <I3)(13) (65) (74) (66) (76) (122) (198) (40) • ••• ~•• •• • ns — ns ns * ns ns LepiagrionLeptagrion 82 0 0 2 0 3.5 0 15.5 0.5 absent (33) (27) (96) (22) (41) (35) (129) (21) 1 All ranges begin at zero. 2 the number of Oligochaetes were onlyrecognized in dry-season samples, therefore plant samples for this taxon (only) is, top to bottom; II, 38, 25, 40. 3 Levels ofsignificance tested by Mann-Whitney U (2-tailed): • =P < 0.05, *• = P < 0.01, •••= not P < 0.001, ns = significant. Leplagrion siqueirai in Aechmea bromeliads 197 association and T. a significant (P < 0.05) negative between L. siqueirai haemorrhoidalis (LOUNIBOS et al., in press). We have separated the presence-absence data by plant species, under which conditions the negative associations are no longer significant for A. nudicaulis (chi-squared = 1.42, I df) = or A.

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