Addressing biodiversity knowledge shortfalls in New World Helicopsychidae (Insecta, Trichoptera): Potential distribution, environmental gradients, and identification of conservation and research priority areas

PLOS One | https://doi.org/10.1371/journal.pone.0327580 July 28, 2025 3 / 22 in several aspects [e.g., 18–22]. Knowledge about Trichoptera species, distribution ranges, and biogeographic patterns is scarce, especially in the Neotropical region (NT) sensu de Moor & Ivanov [20,23–26]. Studies of Trichoptera have focused almost entirely on systematics, with few studies related to biogeography and a much smaller proportion concerned with understanding which factors limit the distribution of groups [25]. However, data related to the biology, environmental and biogeography limits are essential for understanding how species will behave both in scenarios of environmental impacts (e.g., deforestation, burning) and in scenarios of climate change [27]. Especially when it comes to taxa that play a key role in the trophic dynamics of freshwater and adjacent terrestrial ecosystems, such as the Trichoptera [19], and with factors such as temperature, rainfall, and riparian vegetation directly influencing the distribution of species [28]. Despite its importance, it has suffered alarming population declines, 2/3 (68%) of the caddisfly species experiencing population declines, 63% of the species threatened, and a local/regional extinction rate of 6.8% [29]. Among the caddisflies, Helicopsychidae von Siebold, 1856 are represented by two genera, the monotypic Rakiura McFarlane, 1973 (endemic to New Zealand), and Helicopsyche von Siebold, 1856 (circum-global distribution) [30]. Helicopsyche comprises 298 valid species in six subgenera: Cochliopsyche Müller, 1885, Feropsyche Johanson, 1998,

Galeopsyche Johanson, 1998, Helicopsyche, Petrotrichia Ulmer, 1910, Saetotricha Brauer, 1865 [31]. In the Neotropical (NT), Nearctic (NA) and Patagonian (PA) regions (sensu de Moor & Ivanov) have 146 valid species in two subgenera, H. (Cochliopsyche), with 17 Neotropical species, and H. (Feropsyche), with 129 species (including three fossil species from the Dominican Republic) widely distributed throughout the NW (NA with 13, NT with 125, and PA with two valid species) [31,32]. Helicopsyche is a genus recognized by larval cases built with sand grains, helically organized, and resembling snail shells [33]. Like most caddisflies, the immature stages live in freshwater ecosystems and, after completing the metamor- phosis, they emerge as winged adults associated with riparian forests [34]. Due to its wide distribution and occurrence in different freshwater environments of the NW [35], the genus represents a good biological model for initial studies that seek to identify and define distributional patterns of amphibiotic insect groups. Furthermore, understanding how these species are distributed and grouped can provide subsidies for the identification of under-sampled areas [36]. The subgenus Feropsyche was revised by Johanson (2002), and subsequent studies have primarily focused on spe- cies descriptions and new distribution records [e.g., 32,37–40]. In contrast, the subgenus Cochliopsyche has received comparatively less attention following its revision by Johanson (2003) [41], with most contributions limited to new distribu-

tion records [e.g., 42–44] and the description of a single new species, Helicopsyche (Cochliopsyche) nyurga Oláh & Oláh, 2022. The taxonomic literature on Helicopsyche also reveals a notable bias toward male specimens [33,45]. Species description based only on male adults is a quite frequent practice in caddisfly taxonomy and accurately sepa- rates species [24], as in some other insect orders [7]. For the most caddisflies, immature stages and females are unknown (an average of <15% of the immatures are known, and in 41 Neotropical genera, the immature stages are unknown) [46], demonstrating a knowledge shortfall related to other semaphoronts. This causes a genuine problem since most adult collections use light traps, which collect more adult females than males [47]. In addition, Helicopsyche species are mainly reported exclusively to type localities and/or adjacent localities (like the same district) [e.g., 32]. The combination of these two factors inevitably leads to knowledge shortfalls [8]. Understanding distribution patterns, environmental gradients, and biodiversity hotspots—along with identifying Biodiver- sity Knowledge Shortfalls (KBS) and prioritizing research efforts—provides crucial insights for addressing Wallacean and Hutchinsonian shortfalls and informs strategies for tackling other BKS. Additionally, this information forms a foundation for developing new research proposals, conservation actions, and enhancing understanding of biogeographic patterns

and the relationships between species and regions for New World Trichoptera. Within this framework, this study aimed to identify distribution patterns, establish environmental gradients, and model the distribution of Helicopsychidae subgenera in the New World.