Changes in the Understanding of Fungal Diversity Based on Research in the Tropics

Abstract

Fungi are representative one of the world’s eukaryotic kingdoms and play an important role in various ecosystems. For example, they are responsible for breaking down organic matter and recycling nutrients (as decomposers), mutualistic interactions with plants (as mycorrhizae and endophytes) and causal agents of disease (as pathogens) [1–3]. The question of how many fungal species actually exist is indisputably important. Over the past two decades, a conservative estimate of 1.5 million species of fungi has been reported globally [4]. However, this estimation has been based on extrapolations derived from several independent sources of data and would still not include sequence data that have been derived from environmental DNA sequences. Notably, there is still no comprehensive database pertaining to fungal diversity in tropical areas. New fungal taxa have already been described and a number of recent studies have revealed that fungal diversity may actually exceed previous estimates. During the last decade, with the use of morphological and molecular approaches, new fungal species have been described. However, the presence of cryptic species or species complexes has frequently led to overestimated geographic distributions of certain taxa. Accordingly, new fungal species are usually discovered in hotspot areas or areas where most fungal taxonomists are presently working. Thus, global fungi species records have been revised to between 2.2 and 3.8 million species [5,6]. The rate of recovery for new fungal species has been reported in known hot spot areas to be more than 2,000 species per year [6]. A comparison of new fungal species described from each continent in 2017 [6] and 2019 [7] is presented in Figure 1. The majority of new fungal species has been recorded from Asia, followed by Europe, America, Oceania, Africa, and Antarctica. However, less than 10% of the fungal species in the world have been accurately described [5]. Remarkably, the increasing trend in newly recorded fungal species is expected to continue to rise in the future.