Quantifying research interests in 7,521 mammalian species with h-index: a case study

Abstract

Background: Taxonomic bias is a known issue within the field of biology, causing scientific knowledge to be unevenly distributed across species. However, a systematic quantification of the research interest that the scientific community has allocated to individual species remains a big data problem. Scalable approaches are needed to integrate biodiversity data sets and bibliometric methods across large numbers of species. The outputs of these analyses are important for identifying understudied species and directing future research to fill these gaps.

Findings: In this study, we used the species h-index to quantity the research interest in 7,521 species of mammals. We tested factors potentially driving species h-index, by using a Bayesian phylogenetic generalized linear mixed model (GLMM). We found that a third of the mammals had a species h-index of zero, while a select few had inflated research interest. Further, mammals with higher species h-index had larger body masses; were found in temperate latitudes; had their humans uses documented, including domestication; and were in lower-risk International Union for Conservation of Nature Red List categories. These results surprisingly suggested that critically endangered mammals are understudied. A higher interest in domesticated species suggested that human use is a major driver and focus in mammalian scientific literature.

Conclusions: Our study has demonstrated a scalable workflow and systematically identified understudied species of mammals, as well as identified the likely drivers of this taxonomic bias in the literature. This case study can become a benchmark for future research that asks similar biological and meta-research questions for other taxa.

Keywords: bibliometrics; meta-research; research bias; research on research; scientific mapping; topic modeling.

Figure 1

: Species h-index of mammals. Panel (A) shows 34 mammals with h = 100 or more, representing 6 different orders marked by dots of different colors. Figure in the inset shows the distribution of species h-index of all mammals, with the species scoring above h = 100 or more marked by the red box. Panel (B) shows the mammals with h = 100 or more but removes domesticated species, with 17 species left.

Figure 2

: The changes in mammalian literature from 1940 to 28 April 2021. (A) The number of publications per year for 30 mammalian orders and the proportion of species per order from the collated mammalian data set represented by the doughnut chart, and (B) change in the frequency of publications on 30 mammalian orders present in the data set. Total number of mammalian species analyzed is 7,521.

Figure 3

: Centroids of global distributions of 4,744 mammalian species. (A) The distribution of nonthreatened species listed as “Least Concern”. (B) The distribution of threatened species listed as “Vulnerable”, “Near Threatened”, “Endangered”, “Critically Endangered”, and “Extinct in the Wild”. The species’ corresponding h-index values are illustrated by dot color.

Figure 4

: Relationship between predictor variables and species h-index values. (i) (A) Species average body mass (n = 5,158 species, fitted curves represent 50% quantile for each clade). (B) Median latitude of species geographical distribution (n = 4,435 species, fitted curve from generalized additive model [GAM] with shaded gray area representing 95% confidence interval; density bar on top of the plot illustrates the number of species at each latitude). (C) Human use categories (n = 7,521, No documented use = 6,124 and Use documented = 1,397). (D) Domestication status (n = 7,521 species, Domesticated = 12, Partially domesticated = 136, and Wild = 7,373). (E) IUCN Red List status (n = 5,584 species, Least Concern = 3,152, Near Threatened = 340, Vulnerable = 530, Endangered = 512, Critically Endangered = 208, and Extinct in the Wild = 2). (F) Google Trends index summed for each species (n = 7,521 species, Google Trends index > 0 = 1,323, and Google Trends index = 0 = 6,124 species). Box plots in (C), (D), and (E) show the median, 25th and 75th percentiles, and lower and upper extremes. (ii) Showing the same data as (i), except each species is colored according to their domestication status.