Naturally fragmented landscapes are adequate systems for evaluating patterns and mechanisms that determine species distribution without confounding effects of anthropogenic fragmentation and habitat loss. We aimed to evaluate an ant metacommunity’s spatiotemporal patterns in montane forest islands amid a grassland-dominated matrix. We assessed these patterns by deconstructing the ant metacommunity into forest-dependent and habitat generalist species. We sampled twice a year (summer and winter) over 2 years (2014 and 2015), using soil and arboreal pitfall traps, in fourteen forest islands (varying in size, shape, and connectivity) in the Espinhaço Range Biosphere Reserve, Brazil. We evaluated the relationship between ant species richness, composition (β-diversity), and predictor variables of forest island structure (canopy cover and understory density) and landscape structure (forest amount, number of forest islands, and shape). We sampled 99 ant species, 66.7% of which were classified as forest-dependent and 33.3% as habitat generalist species. We found that ant β-diversity was higher in space than in time, and that species composition variation in time (temporal β-diversity) differed between ant species groups. Both ant groups responded differently to forest island and landscape structure characteristics. Landscape structure seems to act as a spatial filter and the forest islands’ local characteristics as an environmental filter, which jointly determine the local and regional diversity. We demonstrate the importance that forest archipelagos pose to ant metacommunity’s structure and dynamics in montane tropical regions. Mountaintop conservation and management strategies must consider the forest island archipelago to maintain the biodiversity and the functioning of these systems.

自然破碎的景观是评估确定物种分布的模式和机制的适当系统，而不会混淆人为破碎和栖息地丧失的影响。我们的目的是在以草原为主的矩阵中评估山地森林岛屿中蚂蚁元群落的时空模式。我们通过将蚂蚁元群落解构为依赖森林和栖息地的通用物种来评估这些模式。我们在 2 年（2014 年和 2015 年）中每年（夏季和冬季）采样两次，使用土壤和树栖陷阱，在巴西埃斯皮尼亚索山脉生物圈保护区的 14 个森林岛屿（大小、形状和连通性各不相同）中进行采样。我们评估了蚂蚁物种丰富度、组成（β-多样性）、林岛结构（树冠盖度和林下密度）和景观结构（森林数量、林岛数量和形状）的预测变量。我们采样了 99 种蚂蚁，其中 66.7% 被归类为森林依赖物种，33.3% 被归类为栖息地通用物种。我们发现蚂蚁 β 多样性在空间上高于时间，并且蚂蚁物种组之间的物种组成在时间上的变化（时间 β 多样性）不同。两个蚂蚁群体对林岛和景观结构特征的反应不同。景观结构似乎充当空间过滤器，森林岛屿的地方特征充当环境过滤器，共同决定了地方和区域的多样性。我们证明了森林群岛对山地热带地区蚂蚁元群落结构和动态的重要性。山顶保护和管理战略必须考虑林岛群岛，以维持这些系统的生物多样性和功能。