ecology of phasmids - KLUEDO - Universität Kaiserslautern

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Community structure & host range 24 2.4 Discussion This study is the first to demonstrate diversity and distributional patterns of the phasmid community of a tropical rainforest. The phasmid community of BCI was poor in species and in density. Spatially phasmids were largely restricted to forest edge habitats resulting in higher diversity and density compared to the forest understory. While phasmid abundances varied throughout the study period, no seasonal effect on phasmid abundance was detectable. The distribution pattern of phasmid species was clearly linked to restrictions in their host range that seemed to reflect the successional status of host plant species. 2.4.1 Phasmid diversity, density, and distribution With a total of 12 species, the phasmid community of Barro Colorado Island was expectedly low in species richness. Worldwide, the order Phasmatodea contains about 3000 described species that occur mainly in tropical regions (Whiting et al. 2003) and is species poor compared to other insect orders that are highly diverse in herbivores like Lepidopterans, Coleopterans, and - to a lower extent – Orthopterans. For example, on BCI there are approximately 274 species of true butterfly (Lepidoptera, Papilionoidea; DeVries 1994) and 250 species of katydids (Orthoptera, Tettigoniidae; A. Lang, unpublished data). I found reports of 42 phasmid species occurring in Panamá (see Appendix 1 for species and references) whereof BCI accommodates 26 %; plus one species not formerly reported from Panamá (Otocrania sp.). Analysis of collection records (Windsor, Aiello, Berger, unpublished data) indicates that Gamma-Diversity in Panamá is high with discrete regions giving shelter to different phasmid species. Together with the fact that I recorded all but one species previously reported from BCI (Trychopeplus laciniatus; Aiello, unpublished data) I am confident that I assessed the phasmid community adequately. I showed that forest edges and gaps represented important habitats to the majority of phasmid species on BCI. In contrast, the forest understory seemed to provide a suitable habitat for M. diocles only. Higher abundance of insect herbivores in gaps is often inferred from higher herbivore damage on gap-adapted versus understory plant species (Coley 1980, 1982, 1983; Coley & Barone 1996). Smiley (1978) found that Heliconius butterflies were more abundant in young successional than in understory habitats (Table 2-3). My results support this pattern on the phasmid community and species level. In forest edges phasmid density was 35 times, and M. diocles density three times higher than in the understory (cf. Table 2-1). Low densities of phasmids in the BCI forest understory correspond with Elton (1973) who found low total arthropod densities of 0.92 ind.*m -3 in the same habitat (18400 ind.*ha -1 , extrapolated on two meter height; Table 2-4).
Community structure & host range 25 Table 2-4: Densities of phasmids, insects, and arthropods in the understory and in gaps/forest edges of neotropical rainforests and one temperate forest. Region Habitat Density Neotropical, Panamá Puerto Rico gap [ind.*ha -1 ] Studied organisms Reference understory 7.8 Phasmatodea presented study forest edge 274.9 understory 6.7 Metriophasma diocles forest edge 21.5 (Phasmatodea) understory 18000 arthropods Elton 1973 1 understory gap gap 3520 – 6460 2111.1 351.7 57.55 Lamponius portoricensis (Phasmatodea) Agamemnon iphemedeia (Phasmatodea) Willig et al. 1986 1&2 Willig et al. 1993 1 Willig & Camilo 1991 1 Costa Rica understory 0.5 - 1.5 Heliconius cydno Smiley 1978 gap 1.4 – 5.0 H. hecale & H. erato (Lepidoptera) understory 160000 arthropods Janzen & Schoener 1968 1 Guyana understory, seedling foliage Temperate, Switzerland understory, foliage Density [ind*m -2 ] 2.4 insects Basset 1999 3 19 - 78 insects Basset & Burckhardt 1992 3 1 to allow for better comparison density estimates per ha were extrapolated from published data 2 the authors used different calculation methods on their dataset resulting in variation of density estimates 3 densities in these studies are based on sampled foliage area and thus could not be extrapolated Surprisingly, empirical studies assessing arthropod or insect densities of rainforest edge/gap and understory habitat types are rare (for references see Table 2-4), not to mention comparisons of densities between habitats (Smiley 1978). Largely, existing studies focus on the understory including several feeding guilds, or they refer to sampled leaf area and are therefore of restricted comparability (cf. Table 2-4). In addition, densities are site dependant and may enormously differ in magnitude over time (Table 2-4). For example, densities of the Puerto Rican phasmid Lamponius portoricensis in gaps varied
Page 1 and 2: ECOLOGY OF PHASMIDS (PHASMATODEA) I
Page 5 and 6: ECOLOGY OF PHASMIDS (PHASMATODEA) I
Page 7 and 8: Acknowledgements I Acknowledgements
Page 9 and 10: Table of Contents III 3 Life cycle,
Page 11 and 12: List of Figures V List of Figures F
Page 13: List of Abbreviations VII List of A
Page 16 and 17: Introduction 2 Regardless whether s
Page 18 and 19: Introduction 4 Description of phasm
Page 20 and 21: Introduction 6 Solanum and Piper (T
Page 22 and 23: Introduction 8 1.3.4 Data analysis
Page 24 and 25: Community structure & host range 10
Page 46 and 47: Life history & potential population
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Adult female feeding preference & n
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Adult female feeding preference & n
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Predation mediated mortality & migr
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Concluding remarks 91 6 Concluding
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Abstract 93 7 Abstract Herbivory is
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Literature cited 96 Basset, Y. 1997
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Literature cited 98 Brown, B. J., M
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Literature cited 100 Croat, T. B. 1
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Literature cited 102 Hagerman, A. E
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Literature cited 104 Kearsley, M. J
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Literature cited 106 McNeill, S., T
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Literature cited 108 Reich, P. B.,
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Literature cited 110 Strong, D. R.,
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Appendix 113 9 Appendix Please cont
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Appendix 1: Phasmid species previou
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Tabellarischer Lebenslauf Angaben z
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Berger J., Schaefer, M., 1997. Wild
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