THE WESTERN AUSTRALIAN Vol. 29 30th October 2013 No. 2 NOTES ON THE ECOLOGY AND NATURAL HISTORY OF TWO UNCOMMON ARBOREAL AGAMID LIZARDS DIPORIPHORA PARACONVERQENS AND LOPHOQNATHUS LONQIROSTRIS IN THE GREAT VICTORIA DESERT OF WESTERN AUSTRALIA By ERIC R. PIANKA Integrative Biology University of Texas at Austin Austin, Texas 78712 USA Email: [email protected] ABSTRACT Ecological data on Diporiphora paraconvergens and Lophognathus longirostris are presented. Both species are arboreal, with long tails used as counterbalances during climbing. Both species are associated with sandridges. Diporiphora and juvenile Lophognathus live in large shrubs, whereas adult Lophognathus are often found higher up in Marble Gum trees well above ground. Both species frequently forage on the ground. Both are active thermoregulators. Ambient air temperatures average about 25°C and active body temperatures average 33-34°C in both species, and average time of activity is during midday around noon. These lizards are generalized predators that consume a wide range of insects, especially wasps, hemiptera, beetles, ants, mantids and phasmids as well as larvae of various insects. Diporiphora is partially herbivorous and eats both leaves and flowers. Lophognathus consumes katydids and grasshoppers. Both dietary and microhabitat niche breadths are greater than those of many other sympatric lizard species. Mating occurs and eggs are laid during the Austral Spring. Average clutch size is 3 eggs in Diporiphora and 4.4 in Lophognathus, Relative clutch mass of 4 gravid female Lophognathus with eggs in their oviducts is 0.151. 77 INTRODUCTION abundant. Two juvenile The agamid genus Diporiphora Lophognathus, probably not resi¬ dents but rather dispersers, were has undergone recent revision (Doughty et al. 2012) with de¬ pit-trapped 4 km south of Redsands on my B-area (28° 13.5' scription of a new species S. x 123° 55' E.). 1 consider these Diporiphora paraconvergens. Dur¬ ing the Austral Springs and propagules evidence of meta¬ population structure. Similarly, Summers of 1966-68, 1 en¬ countered Diporiphora para¬ Diporiphora were locally extinct at the Redsands study site where convergens and Lophognathus suitable habitat and micro¬ longirostris on two sandridge habitats occur. study sites, the D-area (34 km W. Lorna Glen HS, 26° 14' S. x 121° 13' The Great Victoria Desert of E.) and the E-area (8 km NE Australia is predominantly sandy Dunges Table Hill, 28° 08' S. x with red sands, and supports a 123° 55' E.), both in the Great vegetation consisting mainly of Victoria Desert. In many years of so-called “spinifex” or “porcu¬ subsequent field work at other pine” grasses (genus Triodia) plus sites, I never found any more various species of gum trees Diporiphora but did collect some (Eucalyptus), especially Marble Lophognathus at my long-term Gums (Eucalyptus gonglyocarpa). Redsands study site (10 km WSW Marble Gum trees are the favored Yamarna, 28° 12' S. x 123° 35’ E.), habitat of adult Lophognathus. although they were never very Shrubs including Eremophila, . Figure 1 Diporiphora paraconvergens in typical alert posture in a shrub. 78 Figure 2. Lophognathus longirostris poised in a small desert tree (note its very long tail). Grevillea, Hakea, and Thryptomene summer thunderstorms. Wild¬ also occur and are used by fires are frequently set by juvenile lizards of both species. lightning and vegetation bio¬ Stabilized long red sandridges, mass and cover vary through parallel to prevailing winds are time as plants undergo secondary scattered throughout the Great sucession following fire (Pianka Victoria Desert, particularly in 1996; Pianka and Goodyear 2012). the eastern interior. Extensive areas of flat sandplain occur as well. The region is very hetero¬ METHODS geneous with mixed ecotonal habitats of shrubs, Triodia, My assistants and 1 observed and Acacia, and Eucalyptus on desert collected 37 Diporiphora para- loams. Beard (1974) and Shephard convergens at 2 study areas and 93 (1995) describe and illustrate the Lophognathus longirostris at 4 vegetation of the region. The study sites. These data were climate is an arid continental augmented with limited observa¬ regime, with cool usually dry tions on a few other lizards that winters and warm springs and were not collected. We recorded autumns but quite hot summers. air and body temperatures, times Most precipitation falls during of activity, microhabitat, fresh 79 snout-vent length (SVL), tail Table 1. Numbers and percentages of length, and weight for as many lizards found in different sandridge lizards as possible. Stomach habitat zones. Sample sizes (N) and contents were identified and habitat niche breadths (HNB) are given at bottom of the table. Lizards at an prey volumes estimated for all interface between habitats split in lizards collected. Reproductive half. condition was also recorded: for males, lengths of testes were Habitat Diporiphora Lophognathus measured; for females, egg sizes were measured and numbers N % N % were counted, and whether eggs Flat 0.5 1.3 11 11.8 were ovarian or oviductal was Base 1.5 3.9 12 12.9 noted [some of these data were Slope 8 21.1 13 13.9 Crest 28 73.7 57 61.3 summarized in appendices in Sample (N) 38 93 Pianka (1986)]. Niche breadths HNB. 1.698 2.348 were calculated using the inverse of Simpson’s (1949) index of diversity [D = 1/ Zp.2] where p. is the proportion of resource state i Diporiphora and Lophognathus are arboreal, with very long tails used as counterbalances during RESULTS climbing. They may climb to Habitat increase their visual field as well as to avoid high surface temp¬ Both species are habitat eratures during the heat of the specialists, and seem to prefer day in summer. slopes and crests of sandridges, although Lophognathus has a Microhabitat broader habitat niche breadth and is more frequently found at Both species are usually the base of sandridges or out on associated with large bushes flat sandplains away from (Table 2). In both species, over sandridges (Table 1). 30 % of lizards were above ground when first sighted. Anatomy Lophognathus also frequents trees and they are more often found Diporiphora is smaller (mean SVL = 45.6 mm, adults = 50.4 mm) higher up than Diporiphora. than Lophognathus (mean SVL = 67 mm, adults = 100.3 mm). Thermoregulation Lemale Lophognathus reach sexual Both species are active thermo¬ maturity at about 94 mm SVL. regulators. Body temperatures of No sexual size dimorphism is 32 active Diporiphora ranged from evident in Lophognathus, but 26.3 to 41°C averaging 33.7°C adult female Diporiphora are with a standard deviation of 3.31 larger than adult males (56.5 mm (average air temperature was versus 47.9 mm). 25.1°C with a standard deviation 80 Table 2. Percentages of lizards Diets encountered in 14 different Diporiphora and Lophognathus are microhabitats. Microhabitat niche sit-and-wait ambush predators breadths (MHNB) is given at the with fairly broad diets. They are bottom of the table. omnivorous, eating both plant Micro- Diporiphora Lophognathus and animal foods (Table 3). The habitat most important insect prey item eaten by both species is wasps Open Sun 5.7 6.96 (29% and 20.7%). Both species also Grass Sun 10 3.91 prey on hemipterans (11.2% and Bush Sun 38.6 31.30 13.3% of diets by volume), beetles Tree Sun 2.17 (9.8% and 7.2% of diets by Other Sun 1.4 0.87 volume), as well as larvae of Open Shade 2.61 various insects (8.7% and 9.6% of Grass Shade 1.4 2.17 Bush Shade 10 7.83 diets by volume). Other less Tree Shade 5.65 important prey items include Other Shade 1.4 0.87 ants, mantids and phasmids. Low Sun 17.1 10.87 Diporiphora are omnivorous con- Low Shade 8.6 6.52 High Sun 5.7 9.13 High Shade 9.13 Sample (N) 35 115 Table 3. Percentages of various dietary MHNB 4.7 6.75 items by volume along with total volume and dietary niche breadths. Prey Diporiphora Lophognathus of 6.12). Body temperatures of 76 Category active Lophognathus ranged from Centipedes 0 0.634 24.8 to 45.4°C, averaging 34.3°C Spiders 3.1873 0.9863 with a standard deviation of 3.84 Ants 7.1713 7.2913 (average air temperature was Wasps 20.7171 29.13 25.6°C with a standard deviation Locustids 2.3904 10.391 of 6.26). Body temperature is Roaches 0 0.7045 correlated with air temperature Mantids/ 5.1793 5.3892 (Fig. 3 and Fig. 4). Phasmids Beetles 7.1713 9.7922 These lizards bask when it is cold, Termites 0 2.1134 and seek shade when it is warm. Hemiptera 11.1554 13.3145 During the heat of mid-day, they Diptera 1.1952 2.6418 sometimes climb up above Larvae 9.5618 8.7355 ground and face directly into the Other Insects 3.1873 5.7062 sun, thereby positioning them¬ Vegetation 29.0837 1.6555 selves in cooler air and reducing Other 0 0.0704 heat load. Climbing also increases UnID 0 1.4442 the area of their visual field and Total Volume 2.51 28.39 may help them avoid contact Dietary Niche 6.07 6.95 Breadth with potential predators. 81 42 15 17.5 20 22.5 25 27.5 30 32.5 35 37.5 Ambient Air Temperature Figure 3. Body temperatures plotted against ambient air temperature for 32 active Diporiphora. BT = 22.899 + .436 * AT; IT2 = .517 Figure 4. Body temperatures plotted against ambient air temperature for 76 active Lophognathus longirostris. 82 suming many plant materials, Lophognathus would include both leaves and flower heads, various species of birds of prey which constitute about 29% of especially Brown Falcons and their diet by volume. Katydids Australian Kestrels, bustards, and grasshoppers constitute large snakes, and monitor lizards 10.4% of the Lophognathus diet by Varanus eremius, V. tristis and V. volume. gouldii as well as introduced cats Both dietary and microhabitat and foxes. Both Diporiphora and niche breadths are greater than Lophognathus rely heavily on camouflage to avoid predators, those of many other sympatric typically freezing and holding lizard species (Pianka 2014). very still until the threat goes away. However, if pursued, of Reproduction course they run rapidly away 15 adult male Diporiphora aver¬ from an attacker. Lophognathus aged 47.9 mm in SVL and 9 adult can run bipedally on their hind male Lophognathus with enlarged legs with tails held high as testes found in November and counterbalances. December averaged 101.6 mm in SVL. Average adult female SVL is 56.5 mm in Diporiphora and 99 DISCUSSION mm in Lophognathus. Clutch sizes of 6 female Diporiphora averaged Dietary and microhabitat niche 3. Gravid female Diporiphora were breadths are greater in both found in September, November Diporiphora paraconvergens and and early December. One gravid Lophognathus longirostris than in female Diporiphora was found in many other sympatric lizard January, suggesting that some species. However, because both females could lay a second species are habitat specialists clutch. Gravid female being restricted to sites with Lophognathus contained from 3 to sandridges and are never very 6 eggs (mean 4.44) and were abundant, these two arboreal found in October, November and species were categorized as rare December. Relative clutch mass by Pianka (2014). Both species in Lophognathus is 0.151. Hatch¬ exhibit features suggestive of lings are small (SVL 30-33 mm in metapopulation structure, such Diporiphora and 40-44 mm in as dispersal propagules, local Lophognathus). Juveniles appear to extinctions, and/or being absent grow fast and undoubtedly from sites with suitable habitats suffer fairly heavy mortality. and microhabitats (see Table 4 in These lizards are not social and 1 Pianka (2014)). have never observed courtship or mating. ACKNOWLEDGEMENTS Predation H. L. Dunlap assisted with field Predators on Diporiphora and work. M. E. Egan and T. D. 83 Schultz helped identify stomach DOUGHTY, P., L. KEALLEY, and J. contents. My research has been MELVILLE. 2012. Taxonomic supported out of my own pocket assessment of Diporiphora (Rep- and by grants from the National tilia, Agamidae) dragon lizards Geographic Society, the John from the western arid zone of Simon Guggenheim Memorial Australia. Zoo Taxa 3518:1-24. Foundation, a senior Fulbright PIANKA, E. R. 1986. Ecology and Research Scholarship, the Aus- Natural History of Desert Lizards. tralian-American Educational Analyses of the Ecological Niche and Foundation, the University Re¬ Community Structure. Princeton search Institute of the Graduate University Press, Princeton, New School at The University of Jersey. Texas at Austin, the Denton A. PIANKA, E. R. 1996. Long-term Cooley Centennial Professorship changes in Lizard Assemblages in in Zoology at The University of the Great Victoria Desert: Texas at Austin, the U. S. Dynamic Habitat Mosaics in National Science Foundation, Response to Wildfires. Chapter 8 and the U. S. National Aero¬ (pp. 191-215) in M. L. Cody and J. A. nautics and Space Adminis¬ Smallwood (eds.) Long-term studies tration. 1 thank the staffs of the of vertebrate communities. Academic Department of Zoology at the Press. University of Western Australia, the Western Australian Museum, PIANKA, E. R. 2014. Rarity in and the Western Australian Australian desert lizards. Austral Department of Parks and Ecology 39, in press. Wildlife (previously Department PIANKA, E. R. and S. E. of Conservation and Land GOODYEAR. 2012. Lizard re¬ Management (CALM)). 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