Mangroves are an overlooked hotspot of insect diversity despite low plant diversity

Darren Yeo,Claas Damken,Amrita Srivathsan,Jayanthi Puniamoorthy,Patrick Grootaert,Rudolf Meier,Benoit Guénard,Lena Chan,Rodzay A Wahab,Foo Maosheng,Ang Yuchen

doi:10.1186/s12915-021-01088-z

Abstract

BackgroundThe world’s fast disappearing mangrove forests have low plant diversity and are often assumed to also have a species-poor insect fauna. We here compare the tropical arthropod fauna across a freshwater swamp and six different forest types (rain-, swamp, dry-coastal, urban, freshwater swamp, mangroves) based on 140,000 barcoded specimens belonging to ca. 8500 species.ResultsWe find that the globally imperiled habitat “mangroves” is an overlooked hotspot for insect diversity. Our study reveals a species-rich mangrove insect fauna (>3000 species in Singapore alone) that is distinct (>50% of species are mangrove-specific) and has high species turnover across Southeast and East Asia. For most habitats, plant diversity is a good predictor of insect diversity, but mangroves are an exception and compensate for a comparatively low number of phytophagous and fungivorous insect species by supporting an unusually rich community of predators whose larvae feed in the productive mudflats. For the remaining tropical habitats, the insect communities have diversity patterns that are largely congruent across guilds.ConclusionsThe discovery of such a sizeable and distinct insect fauna in a globally threatened habitat underlines how little is known about global insect biodiversity. We here show how such knowledge gaps can be closed quickly with new cost-effective NGS barcoding techniques.

Highlights

The world’s fast disappearing mangrove forests have low plant diversity and are often assumed to have a species-poor insect fauna
We here document that the insect fauna inhabiting mangroves is rich, and distinct
Accelerating species discovery for arthropods is a pressing task given that many undersampled habitats are disappearing at a much faster rate than tropical rainforests and coral reefs

Summary

Introduction

The world’s fast disappearing mangrove forests have low plant diversity and are often assumed to have a species-poor insect fauna. The losses of mangroves far exceed those of more high-profile ecosystems such as rainforests and coral reefs [26] These losses are further exacerbated by climate change [27], with some simulations predicting a further reduction by 46–59% for all global coastal wetlands by the year 2100 [28]. This is worrying as mangrove ecosystems sequestrate a large amount of carbon per hectare [29]. Mangrove specialists with such adaptations are well known for vertebrates and vascular plants [33, 34], but the invertebrate diversity is poorly known

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Conclusion