Elsevier

Biological Conservation

Volume 144, Issue 9, September 2011, Pages 2362-2368
Biological Conservation

Spatial α-diversity patterns of diverse insect taxa in Northern China: Lessons for biodiversity conservation

https://doi.org/10.1016/j.biocon.2011.06.016Get rights and content

Abstract

Current approaches in terrestrial biodiversity conservation focus predominantly on plants and vertebrates. While these groups account for less than 4% of the estimated global species richness, it is commonly argued that especially the species richness in higher plants is a suitable indicator of overall biodiversity. We tested this assumption, investigating species richness and equitability patterns in three highly species-rich insect families and their links with the vegetation and other environmental factors. Vegetation surveys were combined with pitfall and light trapping to establish the α-diversity of ground beetles, geometrid moths and arctiid moths on 48 plots at varying altitudes between Beijing and the Inner Mongolian Plateau. Soil pH and nutrient status were also recorded. The α-diversity patterns in the three insect families were non-congruent, and links with phytodiversity were weak. The spatial α-diversity patterns in each of the three insect families were significantly correlated with the species density of individual plant families. These links varied between the three insect taxa and were mostly negative in moths. Furthermore, geometrid moth diversity decreased with increasing elevation and decreasing soil pH. Strongly diverging α-diversity patterns across different insect taxa illustrate that it is impossible to find a simple surrogate representing cross-taxon diversity for these highly diverse groups. Furthermore, phytodiversity and vegetation composition appear to play a limited role in governing insect diversity patterns. These results underline the significant risk that current plant-focused approaches in terrestrial biodiversity conservation are inadequate in addressing the conservation needs of the vast majority of species on earth.

Highlights

► α-Diversity in three diverse insect families and links with environment. ► α-Diversity patterns are highly incongruous. ► Links with vegetation diversity are very weak. ► High risk that many current biodiversity conservation approaches are inadequate.

Introduction

Knowledge of spatial diversity patterns is a key prerequisite for the development of effective strategies in biodiversity conservation (Cabeza et al., 2004, Gaston, 2000, Lamoreux et al., 2005). Such knowledge is already widely available for many vertebrate and plant taxa. Nonetheless, recent estimates (Millennium Ecosystem Assessment, 2005) suggest that these taxonomic groups contribute less than 4% of global species richness. On current knowledge, insects are by far the most species-rich group, with their estimated share in global macro-biodiversity exceeding 50%, but huge knowledge gaps currently prevail in relation to their diversity and distribution.

Not least due to their enormous species richness, insects perform a multitude of fundamental roles in ecosystems. They act as herbivores, predators, pollinators and as a food resource for organisms at higher trophic levels. Insects also control many pest species and greatly aid in nutrient cycling (Summerville et al., 2004). It seems logical to conclude that the great knowledge gaps relating to insect diversity, their distribution patterns and the factors causing these patterns need to be addressed to enable the effective conservation of the global species pool and ecosystem functioning (Leather and Quicke, 2010).

One way to address the severe data scarcity on mega-diverse insect groups is to develop biodiversity indicators and surrogate taxa reflecting the overall status of biodiversity. Indeed, a range of biodiversity indicators is already being used. These indicators commonly employ vertebrate and vascular plant taxa (Butchart et al., 2010), with vascular plant diversity in particular often being suggested as an indicator of overall biodiversity (Myers et al., 2000, Xu et al., 2008). Strong positive links between plant diversity and diversity of herbivores and partly also at higher trophic levels are furthermore suggested by experimental evidence (Scherber et al., 2010, Siemann et al., 1998), while studies questioning this proposed positive relationships between plant and invertebrate diversity (Axmacher et al., 2004b, Axmacher et al., 2009; Hambler and Speight, 1995, Hawkins and Porter, 2003, Wolters et al., 2006) have been widely ignored. As Lewinsohn and Roslin (2008) point out, studies directly investigating the proposed positive links between plant diversity and diversity at higher trophic levels in the natural environment are rare, and this is especially true in relation to diverse terrestrial invertebrate taxa. It is also widely unclear if spatial diversity patterns across species-rich terrestrial insect taxa are congruent. However, this congruency forms a logical prerequisite for biodiversity surrogates to work. Consequently, further comparisons of spatial α-diversity patterns across different insect taxa and the nature and strength of their links to the vegetation are urgently needed, and this study provides important insights into these topics.

Despite our general knowledge deficits in relation to highly diverse insect taxa, more detailed data are available for several groups. One such group are ground beetles (Coleoptera:Carabidae), a species-rich family containing more than 40,000 species (Erwin, 1985) whose taxonomy, distribution and ecology are relatively well understood (Lövei and Sunderland, 1996, Niemela, 1996). Ground beetles react with high sensitivity to habitat changes, and their activity-densities can easily be recorded using pitfall traps (Bowie and Frampton, 2004, Liu et al., 2006, Liu et al., 2010, Poole et al., 2003, Thiele, 1977, Vanbergen et al., 2005). They also play important roles in biological pest control, as many ground beetles and their larvae are predatory (Kromp, 1999).

Geometrid moths are another species-rich insect family whose diversity patterns have been extensively studied for example in Southeast Asia (Beck et al., 2002, Intachat et al., 1997, Intachat et al., 1999, Willott, 1999), South and Central America (Brehm et al., 2003, Brehm et al., 2007, Hilt et al., 2006), Australia (Kitching et al., 2000) and Africa (Axmacher et al., 2004a, Axmacher et al., 2004b, Axmacher et al., 2009). More than 21,000 geometrid species are currently known (Scoble, 1999), and their caterpillars use a wide selection of food-plants, with levels of food-plant specialization apparently highly variable across species (Robinson et al., 2010).

Arctiidae are a moth family comprising about 11,000 known species (Watson and Goodger, 1986). Some studies suggest that arctiids profit from anthropogenic disturbances (Kitching et al., 2000, Nöske et al., 2008), possibly due to a high level of polyphagy in many arctiid caterpillars (Holloway et al., 2001). Arctiid moths, and especially members of the subfamily Arctiinae which dominate in our samples, tend to be morphologically more robust than geometrid moths.

Moths have very strong links with the vegetation, as caterpillars and many adult moths depend on plants as a food and nectar source, while moths in return act as important pollinators (Bawa et al., 1985). They can therefore be expected to react particularly sensitive to changes in the vegetation. Nocturnal moths can be sampled effectively on artificial light sources (Muirhead-Thomson, 1991), with weak light sources allowing for standardized sampling of highly localized species assemblages (Beck and Linsenmair, 2006).

The aim of this study is to investigate spatial patterns and correlations in the α-diversity of species-rich insect families and their links to environmental conditions. Connections between insect diversity and the vegetation form a particular focus of this study. This allows us to establish the existence and extend of the suggested positive links between plant and invertebrate α-diversity, with important implications for the validity of the widespread use of plant-based biodiversity indicators and surrogates. The soil nutrient status is well known to alter plant defence mechanisms against herbivore attack, which consequently alters the structure of the herbivore community (Campo and Dirzo, 2003, Coley et al., 1985, Siemann 1992). Soil nutrients were therefore included in our study to establish if they exert a significant influence also on the α-diversity of different insect families.

Section snippets

Study area and site selection

The study area is located in the mountain ranges stretching from Beijing in the south to the Inner Mongolian Plateau in the north. Geographically, this region falls within the transition zone between the sub-humid monsoon climate of the North China Plain and the semi-arid steppe climate of the Mongolian Plateau. Maximum precipitation is encountered during the summer months, while winter conditions are extremely cold and dry. The entire region has experienced severe habitat degradation in the

Results

A total of 410 plant species belonging to 244 genera and 69 families were recorded in the study area. The pitfall traps contained 3663 ground beetles, which were subsequently divided into 59 species and 14 morpho-species. The light traps caught 14,692 geometrid moths, which were divided into 96 species and 14 morpho-species. Light trap samples also included 1543 arctiid moths representing 19 species and one morpho-species (see Table S1 in Supporting information).

Discussion

Our results provide a clear indication that spatial α-diversity patterns diverge strongly between different insect taxa, and that they also vary significantly in relation to their associations with the vegetation and other environmental parameters. These findings lend support to the increasing number of studies reporting missing or weak positive links in diversity patterns between invertebrate taxa and other taxonomic groups (Axmacher et al., 2004b, Axmacher et al., 2009, Basset et al., 2008,

Conclusion

Overall, it appears increasingly clear that vegetation composition and phytodiversity play a subordinate role in explaining the diversity patterns of herbivorous and predatory insects. With many current approaches in terrestrial biodiversity conservation focused on plants and vertebrates, which themselves represent only a minute fraction of global species richness, we are therefore running a severe risk of completely ignoring the conservation needs of the vast majority of species. As diversity

Acknowledgements

We are very thankful to the National Natural Science Foundation of China for their financial support (30570318 and 30800150). We also want to thank Xiaotong Zhang, Xingtong Li and Ying Pan for their great help and assistance in the field and K. Bowers, J. Beck and two unknown reviewers for their helpful comments on the manuscript.

References (81)

  • J.C. Axmacher et al.

    Habitat type modifies geometry of elevational diversity gradients in geometrid moths (Lepidoptera: Geometridae) on Mt. Kilimanjaro, Tanzania

    Tropical Zoology

    (2008)
  • J.C. Axmacher et al.

    Notes on α- and β-diversity pattern of selected moth families

  • J.C. Axmacher et al.

    Diversity of geometrid moths along an Afrotropical altitudinal rainforest transect

    Diversity and Distributions

    (2004)
  • J.C. Axmacher et al.

    Diverging diversity patterns of vascular plants and geometrid moths during forest regeneration on Mt. Kilimanjaro, Tanzania

    Journal of Biogeography

    (2004)
  • J.C. Axmacher et al.

    Determinants of diversity in afrotropical herbivorous insects (Lepidoptera: Geometridae): plant diversity, vegetation structure or abiotic factors?

    Journal of Biogeography

    (2009)
  • Y. Basset et al.

    Changes in arthropod assemblages along a wide gradient of disturbance in Gabon

    Conservation Biology

    (2008)
  • K.S. Bawa et al.

    Reproductive biology of tropical lowland rain forest trees. II. Pollination Systems

    American Journal of Botany

    (1985)
  • J. Beck et al.

    Explaining the elevational diversity patterns of geometrid moths from Borneo: a test of five hypothesis

    Journal of Biogeography

    (2008)
  • J. Beck et al.

    Drivers of moth species richness on tropical altitudinal gradients: a cross-regional comparison

    Global Ecology and Biogeography

    (2009)
  • J. Beck et al.

    Feasibility of light-trapping in community research on moths: attraction radius of light, completeness of samples, nightly flight times and seasonality of Southeast-Asian hawkmoths (Lepidoptera: Sphingidae)

    Journal of Research on the Lepidoptera

    (2006)
  • J. Beck et al.

    From forest to farmland: diversity of geometrid moths along two habitat gradients on Borneo

    Journal of Tropical Ecology

    (2002)
  • J. Beck et al.

    Links between the Environment, Abundance and Diversity of Andean Moths

    Biotropica

    (2011)
  • J. Belmarker et al.

    Cross-scale variation in species richness-environment associations

    Global Ecology and Biogeography

    (2011)
  • M.H. Bowie et al.

    A practical technique for non-destructive monitoring of soil surface invertebrates for ecological restoration programmes

    Ecological Management & Restoration

    (2004)
  • G. Brehm et al.

    Unique elevational patterns of geometrid moths in an Andean montane rainforest

    Ecography

    (2003)
  • G. Brehm et al.

    The role of environmental and mid-domain effect on moth species richness along a tropical elevational gradient

    Global Ecology and Biogeography

    (2007)
  • S.H.M. Butchart et al.

    Global biodiversity: indicators of recent declines

    Science

    (2010)
  • M. Cabeza et al.

    Combining probabilities of occurrence with spatial reserve design

    Journal of Applied Ecology

    (2004)
  • J. Campo et al.

    Leaf quality and herbivory responses to soil nutrient addition in secondary tropical dry forests of Yucatan, Mexico

    Journal of Tropical Ecology

    (2003)
  • Z.Q. Chen et al.

    Development of land desertification in the Bashang area in the past 20 years

    Journal of Geographical Sciences (China)

    (2001)
  • Y.M. Chen et al.

    Preliminary study on control measures of soil and water conservation districts in Chongli county, Hebei province

    Research of Soil and Water Conservation (China)

    (2007)
  • P.D. Coley et al.

    Resource availability and plant anti-herbivore defense

    Science

    (1985)
  • R.K. Colwell et al.

    Estimating terrestrial biodiversity through extrapolation

    Philosophical Transactions of the Royal Society, Series B

    (1994)
  • T.L. Erwin

    The taxon pulse: a general pattern of lineage radiation and extinction among carabid beetles

  • E. Fournier et al.

    Effects of newly planted hedges on ground-beetle diversity (Coleoptera, Carabidae) in an agricultural landscape

    Ecography

    (1999)
  • K.J. Gaston

    Global patterns in biodiversity

    Nature

    (2000)
  • N. Gotelli et al.

    Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness

    Ecology Letters

    (2001)
  • C. Hambler et al.

    Biodiversity conservation in Britain: science replacing tradition

    British Wildlife

    (1995)
  • B.A. Hawkins et al.

    Does herbivore diversity depend on plant diversity? The case of California butterflies

    American Naturalist

    (2003)
  • N. Hilt et al.

    Diversity and ensemble composition of geometrid moths along a successional gradient in the Ecuadorian Andes

    Journal of Tropical Ecology

    (2006)
  • Cited by (0)

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