The effect of urbanization and temperature on thermal tolerance, foraging performance, and competition in cavity dwelling ants

Human disturbance including rapid urbanization and increased temperatures can have profound effects on the ecology of local populations. Eusocial insects, such as ants, have adapted to stressors of increasing temperature and urbanization, however these evolutionary responses are not consistent among populations across geographic space. Here we asked how urbanization and incubation temperature influence critical thermal maximum (CTmax) and various ecologically relevant behaviors in three ant species in urban and rural locations in Worcester, MA, USA. We did this by incubating colonies of three species of cavity dwelling ant (Aphaenogaster picea, Tapinoma sessile, and Temnothorax longispinosus) from 2 habitat types (Rural and Urban), for 60-days at multiple temperatures. We found that incubation temperature, urbanization and species of ant all significantly affected overall colony critical thermal maximum. We also found that recruitment time, colonization time and defense response were significantly affected by incubation temperature and varied between species of ant, while recruitment and colonization time were additionally affected by urbanization. These variable changes in performance and competitive traits across species suggest that responses to urbanization and shifting temperatures are not universal across species. Changes in behavioral responses caused by urbanization may disrupt biodiversity, creating unusual competitive environments as a consequence of natural adaptations and cause both direct and indirect mechanisms for which human disturbance can lead to local species extinction.

包括快速城市化与气温升高在内的人类活动干扰，会对本地种群的生态产生深远影响。真社会性昆虫（Eusocial insects）如蚂蚁，已适应了气温升高与城市化带来的胁迫因子，但不同地理区域的种群间，这类进化响应并不一致。本研究旨在探究美国马萨诸塞州伍斯特市城乡生境中，城市化与孵化温度如何影响3种蚂蚁的临界热极限（critical thermal maximum, CTmax）及多种生态相关行为。

我们通过以下方式开展实验：将来自城乡两种栖息地的3种筑洞蚁类（Aphaenogaster picea、Tapinoma sessile与Temnothorax longispinosus）的蚁群置于多个温度梯度下孵化培养60天。

实验结果显示，孵化温度、城市化水平以及蚂蚁物种均会对蚁群整体的临界热极限产生显著影响。我们同时发现，孵化温度会显著影响招募时长、定殖时长与防御响应，且这些指标在不同蚂蚁物种间存在差异；此外，招募时长与定殖时长还会受到城市化水平的影响。

不同物种在性能与竞争性状上的这类差异化变化表明，针对城市化与温度变化的响应并非在所有物种间都具有普遍性。城市化引发的行为响应变化可能会破坏生物多样性，通过自然适应过程形成异常的竞争环境，并通过直接与间接两种途径，使得人类干扰最终导致本地物种灭绝。