Annual Abundance and Population Structure of Two Dung Beetle Species in a Human-Modified Landscape

Abstract

Population studies are essential for understanding different aspects of species’ biology, estimating extinction probability, and determining evolutionary and life history. Using the mark-recapture method, we studied the abundance and population structure of dung beetle species (Deltochilum mexicanum and Dichotomius satanas) over one year in a human-modified landscape in Mexico. We captured 1960 individuals with a net recapture rate of 11%. Deltochilum mexicanum had a higher rate of recapture (14%) than Dichotomius satanas (5%). Annual variation in abundance was similar for both species, with maximum abundance occurring in summer and a marked reduction during winter. Deltochilum mexicanum was dominant inside the forest, and its abundance was influenced by vegetation cover, temperature, and humidity. Dichotomius satanas was more frequent outside the forest, and none of the considered environmental variables affected its abundance. The adult sex ratio of Deltochilum mexicanum was female-biased, whereas that of Dichotomius satanas was male-biased. The maximum estimated population size was similar for both species, but Deltochilum mexicanum had a higher number of new individuals and survival rate. Since species with different biological attributes presented a similar pattern of abundance and population structure, we conclude that environmental conditions are the main regulator of dung beetle populations in the human-modified landscape.

Population Dynamics of Six Major Insect Pests During Multiple Crop Growing Seasons in Northwestern New Mexico

“…Finlay-Doney and Walter [9] reported that temperature can stimulate or suppress insect pest genetic potential, mortality and fecundity, and host plants. Danks [10] studied the elements of seasonal adaptation in insects and found the air temperature, air relative humidity, aridity, food availability, sensitivity of environmental signals, interaction among insect species and other factors as responsible elements controlling insect abundance [11,12,13,14].…”

Annual reproductive phenology of the coprophagous beetleDichotomius satanas(Coleoptera: Scarabaeidae, Scarabaeinae) of the cloud forest in eastern Mexico

“…The differences observed in the number of individuals in each stage of sexual maturity suggest that the population dynamic of D. satanas is characterised by high migration (exit of individuals), as has been observed at landscape scale (Barretto et al 2018). Given that approximately 15% of the total number of individuals dissected were mature, we believe that immature and maturing individuals have a greater probability of dispersion at different times throughout the year.…”

“…The results of this study suggest that D. satanas is a protogynous species, as was found for Onthophagus incensus under field conditions (Martínez et al 1998). According to Degen et al (2015), protogyny is characteristic in populations in which males present greater mortality, coinciding with that observed for populations of D. satanas, due to intrasexual competition and greater male mobility (Barretto et al 2018). However, although the phenological cycle of insects is usually characterised by differential emergence between sexes, protogyny is rarely observed (Van Timmerman et al 2000).…”

“…In general, the reproductive phenology of the coprophagous beetles has been studied under controlled laboratory conditions, through observation of morphological changes in the reproductive structures of males and females during the process of sexual maturation (Martínez and Montes de Oca 1988;Hernández-Martínez and Martínez 2003;Huerta et al 2005), while few studies have been conducted under natural conditions (Martínez and Montes de Oca 1994). Although variation in reproductive behaviour among species occurs (Halffter and Edmonds 1982), studies conducted in seasonal environments show that the greatest abundance and the reproductive period are associated with the warmest and most rainy season of the year (Kingston and Coe 1977;Martínez et al 1998;Bang et al 2008;Barretto et al 2018). In order to reach sexual maturity, female coprophagous beetles, in addition to feeding, require an initial copulation to receive seminal liquid from the male that stimulates the physiological mechanism of maturation of the basal oocyte and provokes nesting behaviour (Cruz and Martínez 1998).…”

“…The objective of this study was to describe the annual reproductive phenology of Dichotomius satanas (Harold, 1867) (Coleoptera: Scarabaeidae, Scarabaeinae), a dominant species of the community of coprophagous beetles of the eastern Mexican cloud forest (Pineda et al 2005;Halffter et al 2007;Rös et al 2012), where it is particularly abundant during the rainy season and is thus considered a univoltine species (Barretto et al 2018). Dichotomius satanas is distributed from Colombia to Mexico (Pardo-Diaz et al 2019) and is frequently found in forested areas with different degrees of conservation, as well as in environments derived from human activity such as pastures, secondary vegetation, and plantations (Pineda et al 2005;Halffter et al 2007;Rös et al 2012).…”