Scientific Papers

Habitat heterogeneity and topographic variation as the drivers of insect pest distributions in alpine landscapes


Introduction

Insect pests pose a significant threat to natural resources and food security under landscape changes [1,2,3]. Landscape changes could result in pest outbreaks, and prediction modelling indicated that the probability of pest outbreaks may increase under landscape changes [1,2,4]. Moreover, the simplification of ecological landscapes and fragmentation or elimination of natural habitats cause new environmental disruptions, which have a substantial contribution to changing the interactions between species and increase the sensitivity of ecosystems to insect pests [5,6]. Predicting insect pest species distributions can provide insight into the responses of biodiversity to landscape changes, and develop modelling for ecosystem services across different spatial scales.

Habitat heterogeneity has long been recognized as a key characteristic of ecological landscapes with strong relevance for biodiversity and ecosystem health [7,8]. Experimental and field studies [9,7,10] have shown that habitat heterogeneity can improve biocontrol due to the high percentage of natural habitats, which could provide ample food resources and refuges for natural pests in complex landscapes. Because of their simple ecological landscape, alpine ecosystems may have a limited ability to prevent and control insect pest damage [11,12,13]. Topographic factors have a large potential to affect the distribution pattern of insect pests in alpine landscapes due to changes in hydrological, geomorphological, and biological processes [14,13,15]. A rapid change in climate and land cover can lead to extinction and biodiversity loss that especially affect sensitive alpine landscapes [16,17]. Furthermore, habitat heterogeneity and topographic variation may affect species distributions and diversity along the gradient of landscape variations [1,18,19]. Therefore, it is potential that habitat heterogeneity and topographic variation are the drivers of insect pest distributions in alpine landscapes, as the resulting data would provide insight into biological control.

Alpine ecosystems are vulnerable to landscape variations [17,20]. Numerous prediction studies [21,20] have shown that alpine ecosystem functions and services may be lost under landscape variations. For example, habitat loss and fragments could drive species redistribution, which may negatively affect biodiversity [22,23]. The negative effects of rapid environmental changes on biodiversity may be enhanced in alpine landscapes due to the sensitivity of species distributions to ecological variation (i.e., habitat heterogeneity and topographic variation) [24,23]. Hence, more detailed predictions on the effects of habitat heterogeneity and topographic variation on species distributions in alpine landscapes are required to improve the effectiveness of biodiversity and ecosystem management based on the following two hypotheses.

  • 1)

    Considering the potential relationships between habitat heterogeneity and species diversity, we proposed Hypothesis 1: habitat heterogeneity and topographic variation may affect the probability of insect pest distribution in alpine landscapes. Here, we used species distribution modelling (SDM) to assess the probability of insect pest distribution in alpine landscapes based on occurrence records of insect pest species from Qinghai Province, China [25,26].

  • 2)

    We explored the responses of the probability of insect pest distribution related to habitat heterogeneity and topographic variation in alpine landscapes [27,25]. Effects of environmental conditions on insect pests may depend on a variety of biotic and abiotic factors (e.g., ecological niche, host species, and natural enemy) [28,29,30]. Different insect pest species have their own biotic and abiotic characteristics. Hence, we proposed Hypothesis 2: the responses of the distribution of insect pests to habitat heterogeneity and topographic variation may vary across different insect pest species. We used the jackknife method to determine the contribution of habitat heterogeneity and topographic variation to insect pest distributions in alpine landscapes Thus, we could use habitat heterogeneity and topographic variation as the indicators for pest management in alpine landscapes.



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