A simple hypothesis about distributions is that population size is greatest where environmental conditions are most favorable (Brown 1984). Yet organisms are often excluded from ideal environments by negative biotic interactions such as competition or predation (Buckley and Roughgarden 2005). Organisms can also persistently occur in poor environments due to immigration (Pulliam 1988). Similarly, high extinction rates of parasite populations followed by recolonization, or high adaptability of hosts, can also limit parasite adaptation to their local hosts (Kaltz and Shykoff 1998).  As a result, recent studies have questioned the assumption underlying many macroecological studies that patterns of environmental distribution reflect individual fitness responses to environment (Osorio-Olvera et al. 2019, Holt 2020).  Relatedly, parasite fitness may not always be highest in environments where they are most abundant, though several studies suggest parasite abundance is greater on preferred hosts (Krasnov et al. 2004, Poulin 2005). Higher abundance may translate to higher frequencies of parasite occurrence across sampled localities (Poulin et al. 2012), but this trend is rarely linked to patterns of local adaptation.