DOI: 10.5061/dryad.3r2280gdr
title: Aedes albopictus has not become the dominant species in artificial container habitats in a temperate forest more than a decade after establishment

description: Aedes albopictus (Skuse) is one of the most invasive species globally, and
 has led to rapid declines and local extirpations of resident mosquitoes
 where it becomes established. A potential mechanism behind these
 displacements is the superior competitive ability of Ae. albopictus in
 larval habitats. Research on the context-dependent nature of competitive
 displacement predicts that Ae. albopictus will not replace native Aedes
 triseriatus (Say) in treeholes but could do so in artificial container
 habitats. Ae. albopictus remains rare in temperate treeholes but less is
 known about how Ae. albopictus fares in artificial containers in forests.
 Tyson Research Center (TRC) is a field station composed of mostly
 oak-hickory forest located outside Saint Louis, MO. The container
 community has been studied regularly at TRC since 2007 with permanently
 established artificial containers on the property since 2013. Ae.
 albopictus was detected each year these communities were sampled; however,
 its abundance remains low and it fails to numerically dominate other
 species in these communities. We present data that show Ae. albopictus
 numbers have not increased in the last decade. We compare egg counts from
 2007 and 2016 and combine larval sample data from 2012-2017.We present
 average larval densities and prevalence of Ae. albopictus and two
 competitors, Ae. triseriatus and Aedes japonicus (Theobald) as well as
 monthly averages by year. These data highlight a circumstance in which Ae.
 albopictus fails to dominate the Aedes community despite it doing so in
 more human-impacted habitats. We present hypotheses for these patterns
 based upon abiotic and biotic environmental conditions.
description: <b>Egg sampling; 2007
 and 2016</b> Eggs were
 collected using identical protocols during 2007 and 2016 to compare the
 average number of <i>Ae. albopictus</i> eggs laid at TRC when
 these communities were first studied (2007) and a decade later (2016).
 Fifty 500 ml black plastic cups lined with seed germination paper (thus
 forth “egg papers”) were attached to trees 1-2 meters from the ground and
 filled with 270 ml tap water and 30 ml of a 10%, by weight, hay infusion
 incubated for 7 days. Cups were placed along five transects, in
 approximately the same locations for both years. Per transect, 5 traps
 were placed along the forest edge on service roads (2 m wide, full canopy)
 50 meters apart, and 5 were placed 50 meters into the forest. Egg papers
 were collected on three dates, at weekly intervals, within each of three
 collection periods; early June, mid-July, and late August after each paper
 had been in the field for four days (450 samples/year). Egg papers were
 incubated in an environmental chamber for 4-7 days before being placed in
 0.35 g/L nutrient broth solution (Difco<sup>TM</sup>) to
 stimulate egg hatching. Larvae were identified to species as third or
 fourth instars. No attempt was made to count total eggs laid or to
 identify unhatched eggs. Larvae identified as <i>Ae.
 albopictus</i> are reported as the number of <i>Ae.
 albopictus</i> eggs laid per day. We used a Generalized Linear Mixed
 Model (GLMM) with a zero inflated Poisson error distribution using eggs
 laid per day as the response variable, year and month as independent
 variables, and transect as a random effect (PROC GLIMMIX). The three
 samples within each month and the forest vs. edge samples were collapsed
 into “month”. We also
 analyzed proportion of egg papers with <i>Ae.
 albopictus </i>present using a GLMM (PROC GLIMMIX) with a binary
 distribution (present vs. absent) testing for effects of years, months,
 and interaction, with transect as a random variable. Both analyses were
 performed in SAS 9.4.<br>   <b>Larval sampling: 2007
 and 2012-2017</b> To compare the
 larval densities and frequency of collection of common species at TRC we
 summarized the data collected from larval samples from 2012-2017. These
 data were collected from black plastic containers which always received an
 initial input of rainwater and oak leaf detritus. Each year of data
 originates from a different field experiment, with different
 manipulations, designed to answer research questions not directly related
 to this study and is repurposed here (Westby and Juliano 2017, Juliano et
 al. 2019, Westby et al. 2019). Details about the experimental
 manipulations and sampling schedule can be found in the supplemental file.
 Depending on the year, larval communities were either subsampled
 destructively or the entire community was identified and returned to its
 container. To standardize the data, accounting for differences in methods,
 we present the prevalence of each <i>Aedes</i> species in
 samples from containers by month with the years 2012-17 combined, in
 addition to prevalence for the dominant predator <i>Toxorhynchites
 rutilus </i>(Coquillett). We also present mean densities
 (larvae/liter) from containers where the focal species was present. We
 present the average monthly <i>Ae. albopictus</i> larval
 density for every liter of water sampled (e.g., not excluding samples
 where they absent) and prevalence by month for all the years including
 larval samples collected in 2007 (not included in the prevalence and
 density data above). Larval samples were collected in 2007 but volumes
 were not recorded. We limited our
 statistical treatment to the egg sampling data collected in the two years
 in which we replicated field methods exactly (2007 v. 2016). For other
 years, the data were collected differently or there were not enough data
 points in each month for each manipulation in all years to include in a
 statistical model. We also present no data on <i>Culex</i> as
 they were rare in larval samples later in the season when we began to
 detect <i>Ae. albopictus</i>.