The Haeckelian shortfall or the tale of the missing semaphoronts

Abstract

When faced with the daunting and exciting task of studying biodiversity, one must necessarily come to terms with a few challenging knowledge gaps, the so‐called biodiversity shortfalls. Given that biodiversity is inherently multidimensional, it seems rather natural to admit that hitherto unrecognized shortfalls, on other distinct aspects of biodiversity, should be considered. Here, we introduce the Haeckelian shortfall, which has as its nexus organismal ontogeny, and refers to the relative scarcity of knowledge about the distinct semaphoronts of a substantial fraction of all known species. The Haeckelian shortfall has a profound relevance on the matter of total evidence, in the context of systematics, besides several indirect effects on the other shortfalls, as they all are intimately interconnected. The importance of studying distinct semaphoronts is crystal clear: Besides the purest and most descriptive access to the ontogeny of species (the idiographic aspect), assessing those semaphoronts will certainly promote the advancement of relevant nomothetic knowledge, contributing to an increasingly meaningful eco–evo–devo. Overcoming the Haeckelian shortfall is certainly a major challenge in our task of knowing and preserving biodiversity.

Linnean and Wallacean shortfalls of Leptophlebiidae (Ephemeroptera: Insecta) in the Brazilian Amazon

“…Considering this, another challenge hindering advances in the taxonomy of Leptophlebiidae and the order Ephemeroptera is the “Haeckelian deficit” (Faria et al, 2020) (i.e., lack of knowledge about all life stages of species). In many cases, only one life stage is formally described (e.g.…”

Molecular evidence for deeper diversity in Australian Tanypodinae (Chironomidae): Yarrhpelopia and related new taxa

“…Conversion of codes to formal taxonomy is time-consuming, yet all semaphoronts should be described in taxonomic and biodiversity studies, as is well argued by Faria et al (2020). With the advent of molecular systematics and funding to compare the phylogeny of all Tanypodinae, progress came from 'reciprocal illumination' in synthesising molecular data and morphology of all stages.…”

Expanding the Mesozoic Record of Early Brachyceran Fly Larvae, including New Larval Forms with Chimera-Type Morphologies

“…Understanding the peculiarities of each life stage is therefore key to uncovering the ecological network of these ecologically important animals. It has been widely recognized that we lack information about the immature stages of most extant holometabolans, with a large part of the species only known as adults [6][7][8]. Going back to the fossil record, this problem worsens considerably given that we have even fewer tools to associate the different life stages.…”