Published online October 24, 2023
Journal of Ecology and Environment (2023) 47:15
1Ecological Observatory Team, National Institute of Ecology, Seocheon 33657, Republic of Korea
2Ecological Technology Research Team, National Institute of Ecology, Seocheon 33657, Republic of Korea
Correspondence to:Sungbae Joo
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Many insectivorous bats have flexible diets, and the difference in prey item consumption among species is one of the key mechanisms that allows for the avoidance of interspecies competition and promotes coexistence within a microhabitat. In Korea, of the 24 bat species that are known to be distributed, eight insectivorous bats use forest areas as both roosting and foraging sites. Here, we aimed to understand the resource partitioning and coexistence strategies between two bat species, Myotis ikonnikovi and Plecotus ognevi, cohabiting the Mt. Jumbong forests, by comparing the differences in dietary consumption based on habitat utilization.
Results: Upon examining their dietary composition using the DNA meta-barcoding approach, we identified 403 prey items (amplicon sequence variants). A greater prey diversity including Lepidoptera, Diptera, Coleoptera, and Ephemeroptera, was detected from M. ikonnikovi, whereas most prey items identified from P. ognevi belonged to Lepidoptera. The diversity index of prey items was higher for M. ikonnikovi (H’: 5.67, D: 0.995) than that for P. ognevi (H’: 4.31, D: 0.985). Pianka’s index value was 0.207, indicating little overlap in the dietary composition of these bat species. Our results suggest that M. ikonnikovi has a wider diet composition than P. ognevi.
Conclusions: Based on the dietary analysis results, our results suggests the possibility of differences in foraging site preferences or microhabitat utilization between two bat species cohabiting the Mt. Jumbong. In addition, these differences may represent one of the important mechanism in reducing interspecific competition and enabling coexistence between the two bat species. We expected that our results will be valuable for understanding resource partitioning and the coexistence of bats inhabiting the Korean forests.
Keywords: dietary comparison, Myotis ikonnikovi, Plecotus ognevi, resource partitioning
Early ecological models based on intra- and inter-specific competition suggested that species responses to the environment must be sufficiently differentiated from multidimensional ecological resources to enable their stable coexistence (Andriollo et al. 2021; Bazzaz and Catovsky 2001; Finke and Snyder 2008). Resource use and partitioning are two of the main factors explaining ecological differences that lead to species coexistence (Finke and Snyder 2008; MacArthur 1984; Schoener 1974).
Bats serve as a fascinating example to explain resource partitioning in ecological communities, as they tend to form communities based on morphological and ecological similarities (Arrizabalaga-Escudero et al. 2018) and have a flexible diet that varies among different species (Clare et al. 2014; Salinas-Ramos at al. 2015). Several studies have investigated food consumption and resource partitioning in insectivorous bat species (Andreas et al. 2012; Heim et al. 2021; Whitaker 2004). In Central Europe, a study comparing the dietary composition of three foliage-gleaning bat species (
In Korea, of the 24 bat species that are known to be distributed (Yoon et al. 2016) only 12 have been identified in the Korean forests through trapping and echolocation surveys (Han at al. 2012). Excluding some of the cave-dwelling bats (such as horseshoe bats, long-fingered bats, and greater tube-nosed bats), it is estimated that approximately eight bat species use forest areas as both roosting and foraging sites. These bats inhabiting the Korean forests are classified as insectivorous bats (Han at al. 2012). Two forest-dwelling bat species,
In this study, we compared the dietary composition of two forest-dwelling bat species,
This study was conducted on Mt. Jumbong (128˚25´–128˚30´ E, 38˚0´–38˚5´N) at the southern end of the Seoraksan National Park, South Korea. The area around Mt. Jumbong is one of the long-term ecological research sites in Korea, where research has been conducted since the first stage of the national long-term ecological monitoring project in 2005. Additionally, this area has been designated as a nature reserve and Forest Genetic Resource Reserve by the Korean government. This study was conducted at two different sites (Danmokryeong and Gombaeryeong) near the northern and eastern valleys of Jeombongsan Forest Ecological Management Center. These areas are located at an altitude of 740 m and consist mainly of deciduous broad-leaved forests dominated by oak trees. Previous research on insects revealed the identification of more than 60 species of moths, with belonging to the Noctuidae family (23 species) being the most frequently observed in Mt. Jumbong (Cho 2013). Moths are generally known to be one of the main food sources for forest bats. Access to hikers is strictly limited after 4 p.m., which makes it a suitable area for studying forest bats that are not affected by human activity.
Bat capturing was carried out in June and July 2017 at Danmokryeong and Gombaeryeong in Mt. Jumbong area based on the entry and research permission granted by the Korea Forest Service granted permission (Fig. 1). To capture bats, mist nets were installed within a radius of 50 m around the points estimated to be the main moving routes of bats. Two mist nets, 12 m in width and 3.2 m in height, were installed in the forest valleys for each site, covering a total area of 76.8 m2. Additionally, three mist nets, 6 m in width and 3.2 m in height, were installed between the canopy and upper levels of low-cover herbaceous plants, covering a total area of 57.6 m2. Extra mist nets were installed around the mist net installation site to block the space between trees and shrubs, which promoted bat capture.
The bat capture was conducted for approximately 4 hours after sunset, and the condition of the captured bats was checked every 5 minutes. Each captured bat in the mist net was removed and placed in a cotton bag until release. All the captured bats were identified based on the species and sex and tagged with a metal ring to mark the individual before release.
Fecal samples were collected either directly from the captured bats or from the feces that were collected during their capture in the cotton bag. To minimize sample contamination and degradation, each individual feces were immediately sealed in a 2 mL Eppendorf tube containing 100% ethanol and stored at –20°C until transportation to the laboratory. After transportation, the samples were immediately stored in an ultra-low temperature freezer (–80°C) until DNA extraction.
DNA extraction was performed on less than 200 mg of feces using a QIAamp DNA Fast DNA Stool Kit (Qiagen, Hilden, Germany) following manufacturer’s protocol, after removal of ethanol from the 2 mL Eppendorf tubes. We amplified the cytochrome c oxidase subunit 1 mitochondrial gene (
The libraries for dietary analysis were prepared using the fusion primers modified at the 5´ end by the addition of individual-specific 7-bp Multiplex IDentifiers (MIDs) and adaptors required for the emulsion polymerase chain reaction (emPCR) and the Ion PGM sequencing. All PCR amplifications were performed in 20
Each dataset was pre-processed using Geneious Prime 2022.1. Raw sequences were trimmed based on primer sequences, and filtered when less than 50 bp. Pre-processed datasets were imported into the QIIME2 software platform (version 2022.2.0, https://qiime2.org) (Bolyen et al. 2019), and processed based on Catozzi’s workflow, with some modifications (Catozzi et al. 2019). Briefly, DADA2 was used as the quality filtering method to denoise and dereplicate single-end sequences, and remove chimeras (Callahan et al. 2016); a truncation length of 157 bases was used. The naïve Bayesian classifier was used for taxonomic classification against the COins database (Magoga et al. 2022). After classifying the sequences, amplicon sequence variants (ASVs) that classified as low taxonomic levels (only Phylum level) were not analyzed further.
The proportion of prey items were calculated as both frequency of occurrence (FOO) and relative read abundance (RRA). Percent of occurrence (POO) is the %FOO rescaled so that the sum across all detected dietary items is 100%. All mathematical expressions are as follows (Deagle et al. 2019):
where T is the number of prey items (taxa),
Species diversity was defined as the number of ASVs identified in each sample. The Shannon–Wiener and Simpson’s diversity indices were respectively calculated as follows, based on the POO of prey items (Deagle et al. 2019):
Pianka index of niche overlap index was calculated using “spaa” package (Zhang 2016) from the R software (version 4.1.2). This index represented the degree of dietary overlap between the two bat species, as follows:
An ordination was performed using Bray–Curtis dissimilarity-based principal coordinate analysis (PCoA) using the “vegan” package from the R software (version 4.1.2) based on each fecal sample’s RRA of prey items at the genus level (Oksanen et al. 2022). All statistical analyses were performed using the R software (version 4.1.2).
A total of 1,183,421 raw sequences were obtained from 27 bat fecal samples, and a final 406,304 reads passed trimming and filtering. Of those, 328,785 reads (mean = 15,656 ± 17,433) were derived from 21 individuals of
In total, 403 prey items (ASVs) were identified from the two bat species (Table 1, Tables S1, S2). Of these, 346 ASVs were detected in
The prey item containing 6 orders (54.5%) and 27 families (25.9%) were overlapped between the two bat species (Fig. 3A). Two families, Cossidae and Drepanidae in Lepidoptera, and 16 genera were only detected from
The comparison of prey diversity between the two bat species indicates that
The dietary information of two bat species can provide insights into understanding the mechanisms of stable coexistence through resource partitioning. Resource partitioning is described as one of the mechanisms that prevents competition between species in an ecosystem upon resource limitation (Gómez-Llano et al. 2021; Matthews et al. 2010). Therefore, each species also can adopt a strategy to reduce inter-specific competition by partitioning habitats through spatial or temporal segregation (Matthews et al. 2010). From this perspective, inter-specific spatial partitioning can result in different feeding patterns based on the preferences for selected feeding sites. Our results showed that there were differences in the dietary composition depending on the species, through the comparison of two bat species cohabiting the Korean forests.
The diet consumption of insectivorous bats is primarily determined by their morphological and flight characteristics, echolocation, and foraging strategies (Fenton 1982; Norberg and Rayner 1987). Previously, 14 bats species inhabiting Korea were categorized into three types based on their echolocation call structure (Fukui et al. 2015). Based on that categorization, the two species (
The difference in prey diversity may be interpreted as differences in foraging site preference or differences in space utilization within microhabitats among species. The previous study explains that sympatric living species within the same guild should exhibit differences in at least one niche dimension to avoid competition due to limited food resources, and spatial separation of foraging areas is described as one of the mechanisms to achieve the niche differentiation (Denzinger and Schnitzler 2013). Our results showed that
There are various bat species inhabiting Korea; however, their dietary preferences based on the habitat characteristics are not well understood. This study suggests the possibility of differences in foraging site preferences or microhabitat utilization between two bat species inhabiting the Mt. Jumbong, based on their dietary analysis. Although our study was limited to a specific time period and dietary competition among bat species may vary regionally and seasonally considering insectivorous bats’ relatively flexible diet, our findings contributed to understanding the mechanisms associated with resource partitioning and coexistence among insectivorous bats in Korea. In addition, our results may provide further information on the dietary consumption and resource partitioning of the two bat species inhabiting the forests of Northeast Asia.
Supplementary information accompanies this paper at https://doi.org/10.5141/jee.23.049.
Table S1 Percentage of occurrence data for two bats. Table S2 Relative of abundance data for each samples.
ASV: Amplicon sequence variant
FOO: Frequency of occurrence
RRA: Relative read abundance
POO: Percent of occurrence
PCoA: Principal coordinate analysis
SJ and SSK developed the concept of this study. SJ and IA analyzed and interpreted data regarding dietary composition of two bats. All authors participated in the investigation. SJ was a major contributor in writing, review and editing the manuscript. All authors read and approved the final manuscript.
This research was funded by research projects of the National Institute of Ecology, Republic of Korea, grant numbers NIE-2017-02 and NIE-2023-38.
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
The study was conducted according to the Wildlife Protection and Management Act of the Republic of Korea and the Institutional Research Guidelines of the National Institute of Ecology (RPMT-245, 17 Feb. 2017). All academic survey permission was approved by the Inje National Forest Management Office (No. 2678, 19 April, 2017).
The authors declare that they have no competing interests.