Mediterranean marine protected areas have higher biodiversity via increased evenness, not abundance

1. Protected areas are central to biodiversity conservation. For marine fish, marine protected areas (MPAs) often harbour more individuals, especially of species targeted by fisheries. But precise pathways of biodiversity change remain unclear. For example, how local-scale responses combine to affect regional biodiversity, important for managing spatial networks of MPAs, is not well known. Protection potentially influences three components of fish assemblages that determine how species accumulate with sampling effort and spatial scale: the total number of individuals, the relative abundance of species, and within species aggregation. Here, we examined the contributions of each component to species richness changes inside MPAs as a function of spatial scale.

2. Using standardised underwater visual survey data, we measured the abundance and species richness of reef fishes in 43 protected and 41 fished sites in the Mediterranean Sea.

3. At both local and regional scales, increased sp...