Malaise trap sampling of Hemiptera (Heteroptera; Auchenorrhyncha) was conducted at 500 m intervals along an elevational gradient from 200 m to 3,700 m on the east slope of Mount Wilhelm, Madang Province, Papua New Guinea. Hemiptera had a decrease in morphospecies richness and overall abundance with increasing elevation, however, the Heteroptera did not exhibit either pattern. A few species were relatively abundant at each elevation, whereas the majority of species were represented by ≤5 specimens. Morphospecies richness of Auchenorrhyncha, Cicadomorpha, Fulgoromorpha, Cicadellidae, Cixiidae, and Derbidae also decreased with increasing elevation but abundance decline was not significant due to the large number of specimens captured at 200 m relative to those captured at higher elevations. The percentage of Cicadomorpha specimens decreased with increasing elevation relative to that of the Fulgoromorpha which increased with increasing elevation. Environmental factors that may influence patterns of species richness along the elevational gradient are discussed.
The high organismic diversity of tropical rainforests has been the focus of numerous studies including those that document the diversity of selected taxa and others that seek to elucidate patterns. One type of pattern that emerges is the change in species richness and differences in the composition of insect communities with increasing elevation (
Papua New Guinea, which has the third largest expanse of tropical rainforest in the world (
Studies of taxa within the Hemiptera can provide useful insights about the ecological bases for distribution. Members of the Suborder Auchenorrhyncha are particularly suitable for study because, with the exception of some fungivores, almost all species are sap-feeders on xylem, phloem, or mesophyll as larvae and adults (
Studies of biodiversity and elevational gradients are “natural experiments” that can evaluate ecological theories on climate change as they are keys to understanding how changes in abiotic factors, especially temperature, can affect faunal and floral distribution (
The focus of our study is to document the distribution of Auchenorrhyncha and Heteroptera along a rainforest elevational gradient, to determine the effect of elevation on species richness and abundance, and to discuss the factors affecting distribution.
The study was conducted along an elevational transect on the northeast aspect of Mount Wilhelm in Papua New-Guinea (
Latitude | Longitude | Elevation | ||
---|---|---|---|---|
200 m | Plot A | 5°44′23.63″S | 145°19′47.07″E | 293 m |
Plot B | 5°44′27.71″S | 145°19′45.79″E | 333 m | |
Plot C | 5°44′41.24″S | 5°44′41.24″S | 375 m | |
Plot D | 5°44′14.89″S | 145°19′56.13″E | 214 m | |
700 m | Plot A | 5°43′55.06″S | 145°15′7.79″E | 728 m |
Plot B | 5°43′57.71″S | 145°15′20.04″E | 736 m | |
Plot C | 5°43′57.05″S | 145°15′24.54″E | 757 m | |
Plot D | 5°43′39.91″S | 145°15′28.59″E | 837 m | |
1,200 m | Plot A | 5°43′15.15″S | 145°16′10.07″E | 1,188 m |
Plot B | 5°43′15.68″S | 145°16′13.09″E | 1,201 m | |
Plot C | 5°43′15.24″S | 145°16′17.28″E | 1,223 m | |
Plot D | 5°43′16.93″S | 145°16′13.10″E | 1,199 m | |
1,700 m | Plot A | 5°45′34.45″S | 145°14′8.19″E | 1872 m |
Plot B | 5°45′35.68″S | 145°14′5.02″E | 1,874 m | |
Plot C | 5°45′39.30″S | 145°13′24.72″E | 1,885 m | |
Plot D | 5°45′11.56″S | 145°14′13.32″E | 1,614 m | |
2,200 m | Plot A | 5°45′32.32″S | 145°11′9.84″E | 2073 m |
Plot B | 5°45′36.64″S | 145°11′10.53″E | 2,070 m | |
Plot C | 5°45′39.70″S | 145°11′9.72″E | 2,066 m | |
Plot D | 5°45′26.25″S | 145°11′0.29″E | 2,134 m | |
2,700 m | Plot A | 5°48′54.98″S | 145°9′23.28″E | 2,688 m |
Plot B | 5°48′53.88″S | 145°9′28.66″E | 2,680 m | |
Plot C | 5°48′53.06″S | 145°9′31.80″E | 2,654 m | |
Plot D | 5°48′53.54″S | 145°9′20.17″E | 2,696 m | |
3,200 m | Plot A | 5°48′24.11″S | 145°4′22.52″E | 3,180 m |
Plot B | 5°48′26.71″S | 145°4′25.08″E | 3,076 m | |
Plot C | 5°48′25.00″S | 145°4′19.70″E | 3,182 m | |
Plot D | 5°48′4.65″S | 145°4′8.61″E | 3,361 m | |
3,700 m | Plot A | 5°47′10.11″S | 145°3′35.44″E | 3,750 m |
Plot B | 5°47′13.82″S | 145°3′34.46″E | 3,697 m | |
Plot C | 5°47′8.32″S | 145°3′28.94″E | 3,746 m | |
Plot D | 5°47′27.23″S | 145°3′29.58″E | 3,574 m |
<1,000 m | 1,000–2,500 m | 2,500–3,000 m | >3,000 m | |
---|---|---|---|---|
Max. temperature (°C) | 29.7 | 27.3 | 13.1 | 6.1 |
Min. temperature (°C) | 24.8 | 15.3 | 9.7 | 10.4 |
Mean daily temperature (°C) | 27.38 | 18.34 | 12.12 | 8.38 |
We focused on collecting specimens of the hemipteran suborders Heteroptera and Auchenorrhyncha, although we also collected a few Sternorrhyncha (
Number of | ||
---|---|---|
Taxon | Morphospecies | Specimens |
Heteroptera | 46 | 217 |
Auchenorryncha | ||
Cicadomorpha | ||
Cicadellidae | 303 | 2,544 |
Cicadellidae (larvae) | 23 | 29 |
Cercopidae | 11 | 19 |
Aphroporidae | 1 | 1 |
Cicadidae | 3 | 3 |
Membracidae | 2 | 2 |
Fulgoromorpha | ||
Fulgoromoprha (larvae) | 23 | 47 |
Cixiidae | 53 | 179 |
Delphacidae | 18 | 24 |
Derbidae | 63 | 116 |
Achilidae | 19 | 72 |
Meenoplidae | 6 | 41 |
Dictyopharidae | 2 | 2 |
Flatidae | 5 | 6 |
Issidae | 2 | 2 |
Fulgoridae | 1 | 1 |
Ricaniidae | 1 | 1 |
Sternorrhyncha | ||
Aleyrodoidea | 3 | 3 |
Coccoidea | 1 | 1 |
Psylloidea | 8 | 8 |
Sampling was conducted for 16 days, from 25 October to 10 November 2012 at eight sites placed every 500 m along the elevational transect on the east aspect of Mount Wilhelm. Four Malaise traps (
All specimens were examined at the Muséum National d’Histoire Naturelle (Paris, France) using a Leica MZ16 stereo microscope and identified to morphospecies which is a useful means of identifying large numbers of specimens for ecological studies (
The relationship between elevation and morphospecies richness and abundance was examined using Pearson product moment correlations (
In total, 4,205 specimens were sorted and 713 morphospecies identified; 3,318 specimens representing 596 morphospecies were from the collecting stations on Mount Wilhelm, the remainder were collected in Wanang and used as reference material for our study (
A succession of morphospecies was observed along the elevational gradient. Each morphospecies was rarely collected at more than one elevation (
Elevation (m) | ||||||||
---|---|---|---|---|---|---|---|---|
200 | 700 | 1,200 | 1,700 | 2,200 | 2,700 | 3,200 | 3,700 | |
200 | – | 22 | 5 | 2 | 1 | 0 | 0 | 0 |
700 | 22 | – | 9 | 3 | 0 | 0 | 0 | 0 |
1,200 | 5 | 9 | – | 4 | 0 | 1 | 0 | 0 |
1,700 | 2 | 3 | 4 | – | 6 | 2 | 2 | 0 |
2,200 | 1 | 0 | 0 | 6 | – | 4 | 2 | 0 |
2,700 | 0 | 0 | 0 | 2 | 4 | – | 8 | 0 |
3,200 | 0 | 0 | 0 | 2 | 2 | 8 | – | 5 |
3,700 | 0 | 0 | 0 | 0 | 0 | 0 | 5 | – |
Elevation (m) | ||||||||
---|---|---|---|---|---|---|---|---|
200 | 700 | 1,200 | 1,700 | 2,200 | 2,700 | 3,200 | 3,700 | |
% >5 | 14 | 8 | 6 | 11 | 7 | 8 | 8 | 19 |
% ≤5 | 86 | 92 | 94 | 89 | 93 | 93 | 92 | 81 |
|
163 | 133 | 69 | 72 | 81 | 40 | 52 | 21 |
Analysis via Factorial Components Analysis suggested that there was a succession of morphospecies along the elevational gradient and that there were few species that occurred at more than one elevation (
Each block corresponds to a morphospecies.
Groupings indicate that traps at the same elevation had shared morphospecies.
Overall species richness declined with increasing elevation (
Taxon | Regression |
|
Significance |
---|---|---|---|
|
|||
Hemiptera | 0.83 |
|
|
Heteroptera | 0.11 | – | |
Auchenorrhyncha | 0.83 |
|
|
Cicadomorpha | 0.72 |
|
|
Fulgoromorpha | 0.92 |
|
|
Cicadellidae | 0.72 |
|
|
Cixiidae | 0.71 |
|
|
Derbidae | 0.79 |
|
|
|
|||
Hemiptera | 0.50 | – | |
Heteroptera | 0.07 | – | |
Auchenorrhyncha | 0.51 | – | |
Cicadomorpha | 0.52 | – | |
Fulgoromorpha | 0.43 | – | |
Cicadellidae | 0.52 | – | |
Cixiidae | 0.28 | – | |
Derbidae | 0.34 | – |
Pearson Product Moment Correlation.
(A–C) Elevation and species richness. (D–F) Elevation and abundance. (A, D) Hemiptera. (B, E) Heteroptera. (C, F) Auchenorrhyncha. ∗
The number of specimens captured by the traps appeared to decrease with increasing elevation; however, the correlation was not significant (
Shannon–Weiner Diversity Indices. The highest diversity indices were at the two lowest elevations, which corresponds to the patterns of morphospecies richness and abundance (
Elevation | Shannon Wiener index |
---|---|
200 | 2.558 |
700 | 1.529 |
1,200 | 0.519 |
1,700 | 1.252 |
2,200 | 1.293 |
2,700 | 1.092 |
3,200 | 1.161 |
3,700 | 0.922 |
As indicated above, the Auchenorrhyncha species richness decreased with increasing elevation which led us to further examine species richness patterns in the Cicadomorpha and Fulgoromorpha. Comparison of the proportions of Cicadomorpha relative to Fulgoromorpha suggested that the proportion of Fulgoromorpha increased with increasing elevation. The number of cicadomorph specimens collected at 3,200 m appears to refute this suggestion; however, one cicadellid morphospecies represented 73.5% of all Cicadomorpha collected at this elevation. After removing this morphospecies from the analyses, we found that the Fulgoromorpha represented an increasing proportion of Auchenorrhyncha from ca. 10% at 200 m to ca. 40% at 2,700 m (
(One morphospecies of cicadellid was removed from analysis).
Factorial Components Analysis indicated that there was a sequence of morphospecies corresponding to the elevational gradient of Mount Wilhelm. There was a negative correlation of species richness and elevation for the Hemiptera. There was no relationship between species richness and elevation for the Heteroptera, which may be because of weak association with plant taxa as some were polyphagous and others predaceous (
Abiotic factors that may explain the distribution of the hemipteran taxa include the climatic changes that occur with increasing elevation. Temperature and rainfall decrease significantly from 25–30 °C and ca. 4,000 mm/year at lower elevations to <8 °C and ca. 3,400 mm/year at the highest elevation. These factors directly affect insect development and survival and correspond to the zonation of the vegetation which indirectly affects the distribution of hemipterans (
Species richness decreased with increasing elevation which is similar to patterns observed in several studies (
At every taxonomic level evaluated, there was no correlation between abundance and elevation (
Malaise trap sampling is a very effective means of sampling a portion of an insect community, but as with any single collecting technique, it cannot provide a complete survey of the insect fauna (
Papua New Guinea has a tropical climate with alternating wet and dry seasons. Accurate sampling of hemipterans is a function of the linkage of life cycles to this seasonality. We collected for a short period of time; however, it was done during the optimum collecting period for planthoppers and leafhoppers (
The Cicadomorpha and Fulgoromorpha were the dominant taxa in terms of species richness and abundance (
In the Cicadomorpha, the Cicadellidae consisted of 80% of all Hemiptera collected. In addition, only few Cercopidae, one Aphrophoridae, two Membracidae, and three Cicadidae were collected.
In the Fulgoromorpha, the families with the highest species richness and abundance were the Achilidae, Cixiidae, and Derbidae. The remaining six families included substantially fewer morphospecies and individuals (
Also, these three planthopper families, which represented 79% of morphospecies (
Our inventory of Hemiptera along an elevational gradient on Mt. Wilhelm resulted in finding no pattern of morphospecies distribution and abundance among Heteroptera but declines in morphospecies richness with increasing elevation in the Auchenorrhyncha and its subgroups. The decreasing proportion of Cicadomorpha morphospecies relative to Fulgoromorpha with increasing elevation may be due to differences in host plant communities or larval habitats and therefore warrants further study.
This study was conducted in the framework of “Our Planet Reviewed Papua-New-Guinea 2012–2013” supported by Pro-Natura International, the National Museum of Natural History (MNHN, France), the Institut de Recherche pour le Développement (IRD, France) in partnership with the Royal Belgian Institute of Natural Sciences, the New Guinea Binatang Research Center, the University of Papua New Guinea, and the Divine Word University of Madang and with core funding of Prince Albert II of Monaco Foundation, the Stavros Niarchos Foundation, the Total Foundation, the Fondation d’entreprise EDF, the Fonds Pacifique, Spiecapag, Entrepose Contracting, the New-Caledonia Government, the Reef Foundation and the Belgian National Lottery. The IBISCA expert network, Prof. RK Kitching, and all other participants in this collective effort are thanked for their contribution. For providing his advice and comments on the manuscript, we are grateful to Thierry Bourgoin (MNHN, Paris). And last, but not least, we would like to thank Geoff Martin (NHM, London) who corrected our English.
The authors declare there are no competing interests.
The following information was supplied relating to field study approvals (i.e., approving body and any reference numbers):
Department of Environment and Conservation of Papua New Guinea
Permit no 012297.