Long-Term Functional Dynamics of an Aphidophagous Coccinellid Community Remain Unchanged despite Repeated Invasions

Abstract

Aphidophagous coccinellids (ladybeetles) are important providers of herbivore suppression ecosystem services. In the last 30 years, the invasion of exotic coccinellid species, coupled with observed declines in native species, has led to considerable interest in the community dynamics and ecosystem function of this guild. Here we examined a 24-year dataset of coccinellid communities in nine habitats in southwestern Michigan for changes in community function in response to invasion. Specifically we analyzed their temporal population dynamics and species diversity, and we modeled the community’s potential to suppress pests. Abundance of coccinellids varied widely between 1989 and 2012 and became increasingly exotic-dominated. More than 71% of 57,813 adult coccinellids captured over the 24-year study were exotic species. Shannon diversity increased slightly over time, but herbivore suppression potential of the community remained roughly constant over the course of the study. However, both Shannon diversity and herbivore suppression potential due to native species declined over time in all habitats. The relationship between Shannon diversity and herbivore suppression potential varied with habitat type: a positive relationship in forest and perennial habitats, but was uncorrelated in annual habitats. This trend may have been because annual habitats were dominated by a few, highly voracious exotic species. Our results indicated that although the composition of the coccinellid community in southwestern Michigan has changed dramatically in the past several decades, its function has remained relatively unchanged in both agricultural and natural habitats. While this is encouraging from the perspective of pest management, it should be noted that losses of one of the dominant exotic coccinellids could result in a rapid decline in pest suppression services if the remaining community is unable to respond.

Gut microbiomes of mobile predators vary with landscape context and species identity

“…In contrast, the exotic C. septempunctata and H. axyridis were fatter when their gut bacterial communities were species poor. This finding might reflect that exotic species are better adapted to homogenous conditions in cropland than native species and therefore often dominate coccinellid communities in cultivated habitats (Bahlai, Colunga‐Garcia, Gage, & Landis, ).…”

Shifts in dynamic regime of an invasive lady beetle are linked to the invasion and insecticidal management of its prey

“…Given a new, highly abundant, and highly suitable resource on the landscape, it is unsurprising that we observe higher estimated values of both the intrinsic rate of increase and the carrying capacity for Harmonia (Mignault et al 2006). Harmonia efficiently moves through agricultural landscapes, rapidly locating aphid colonies (Donaldson andGratton 2007, Forbes andGratton 2011), and it may be able to capitalize on soybean aphid as a resource to a greater extent than native lady beetle species (Bahlai et al 2013(Bahlai et al , 2015. Harmonia efficiently moves through agricultural landscapes, rapidly locating aphid colonies (Donaldson andGratton 2007, Forbes andGratton 2011), and it may be able to capitalize on soybean aphid as a resource to a greater extent than native lady beetle species (Bahlai et al 2013(Bahlai et al , 2015.…”

“…Harmonia was first detected in the north central United States in 1992-1994 (Koch et al 2006) and rapidly became one of the most abundant coccinellid species in arable crop landscapes (Colunga-Garcia et Manuscript , Colunga-Garcia and Gage 1998, Bahlai et al 2013. Harmonia's invasion is associated with a long list of negative ecological, economic, and quality of life impacts.…”

“…6 Data were collected at KBS in southwestern Michigan (42824 0 N, 85824 0 W) at 288 m elevation as described in Bahlai et al (2013). 6 Data were collected at KBS in southwestern Michigan (42824 0 N, 85824 0 W) at 288 m elevation as described in Bahlai et al (2013).…”

A sublethal effect on native Anthocoris nemoralis through competitive interactions with invasive Harmonia axyridis

“…However, the spread Correspondence: Andy G. Howe, Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, DK-1958 Frederiksberg C, Denmark. E-mail: andy@ign.ku.dk of invasive H. axyridis in Europe and North America has accompanied declines in the abundance of several native coccinellid species during recent decades (Roy et al, 2012;Bahlai et al, 2013). Asymmetric interspecific interactions in favour of H. axyridis, including intraguild predation (IGP) and exploitative resource competition, are two likely mechanisms behind species declines in invaded habitats (Ware & Majerus, 2008;Evans et al, 2011;Roy et al, 2012).…”