Are the Neglected Tipuloidea Crane Flies (Diptera) an Important Component for Subterranean Environments?

Enrico Lunghi,Yahui Zhao,Gentile Francesco Ficetola,Raoul Manenti

doi:10.3390/d12090333

Abstract

Usually, biospeleological studies focus on cave-specialist taxa showing strong adaptation to the subterranean environment, as their unusual morphological and ecological features represent intriguing case studies. On the other hand, species occurring in subterranean environments but without marked adaptations have been generally overlooked, probably because they are thought to be accidental and not very important for the ecosystem. Particularly exemplificative is the case of Tipuloidea crane flies (Diptera), which although abundant, are rarely considered in biospeleological studies. Here, by analyzing the crane fly occupancy, we observed that individuals occur within the shallowest areas of subterranean environments throughout the year, with a peak of presence during hot season. Crane flies occupy dark and warm areas close to the connection with surface and with smoother walls. Furthermore, we observed that the presence of crane flies is positively related to the abundance and the richness of cave predators, highlighting their importance for the sustainment of the local community. With this study we aim to stimulate future researches on these important, but still neglected cave species.

Highlights

Studies on cave adapted species have gained large interest during the last decades, a trend demonstrated by the growing available literature [1,2,3,4,5]
Given the scarce quantitative ecological information on crane flies, our aim is to study the use of subterranean environments by these species and evaluate its potential relationships with cave-dwelling predators, as crane flies may represent an important food resource in an ecosystem characterized by constant scarcity [1]
We performed a total of 1417 cave sector surveys (Table 1) and we detected crane flies in 709 of them; We performed a total of 1417 cave sector surveys (Table 1) and we detected crane flies in 709 both the number of occupied sectors and their average depth increased during the hot season (Figure 2)

Summary

Introduction

Studies on cave adapted species have gained large interest during the last decades, a trend demonstrated by the growing available literature [1,2,3,4,5]. The high interest in subterranean environments and its biota is often related to the peculiar study-cases offered to taxonomists, ecologists, and evolutionary biologists [6]. The appearance of troglomorphic characters (e.g., reduction in pigmentation, anophthalmia, and elongation of appendages) is related to the peculiar ecological conditions of subterranean environments, which are very different from those found in any surface ones [1]. The subterranean environments show high stability and have a natural microclimatic gradient making them an excellent natural study-system [10,11,12]. The most obvious difference is the lack of light, a condition which contributes in reducing the fluctuation of the subterranean microclimatic conditions, and impedes the colonization of plants, strongly limiting the availability of Diversity 2020, 12, 333; doi:10.3390/d12090333 www.mdpi.com/journal/diversity

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Conclusion