Hybridization and contemporary evolution in an introduced cichlid fish from Lake Malawi National Park.

Rapidly evolving systems offer the chance to observe genetic and phenotypic change in real time. We exploit a well-characterized introduction of cichlid fish into Lake Malawi National Park to document a short history of habitat colonization and the evolution of genes and colour pattern. In the early 1960s, a fish exporter introduced individuals of Cynotilapia afra to a single site (Mitande Point) of Thumbi West Island and, as late as 1983, the species was confined to this location. In 2001, C. afra had colonized the entire perimeter of Thumbi West. In July of that year, we sampled C. afra individuals from six sites around the island and scored variation in dorsal fin colour as well as allelic diversity at six microsatellite loci. We found that, in two decades, C. afra had diverged into genetically distinct, phenotypically different northern and southern populations. We observed a high proportion of hybrids between the introduced C. afra and the native Metriaclima zebra on the southern coast of Thumbi West, and speculate that hybridization is facilitated by low water clarity at these windward sites. The short history of C. afra at Thumbi West is a microcosm of contemporary evolutionary divergence and may provide the opportunity to study the process from start to finish in genetic detail.

Can we identify the factors influencing the burden on family members of patients with schizophrenia?

A growing number of studies reflects an increasing growing interest in the burden on the family (BF) of sufferers from schizophrenia. Many of these studies aim at revealing and identifying the variables that determine BF. This review compares and discusses the results of these studies. Although many variables, such as the diagnosis and symptoms of the patient, the duration of the illness, the treatment setting (outpatient/inpatient), the family relationship between the patient and the relative, and the type of family intervention (counselling and psycho-education) are examined in various studies, there is little consensus on which factors determine the extent and/or pattern of BF. In our opinion, this lack of consistency is mainly caused by: (1) the varieties of definitions and operationalizations of BF employed; (2) the fact that most studies examine only one or just a few variables, so that variables other than those examined may have varied between studies; and (3) the difference in the periods of time discussed in the different studies. To gain more insight into the factors that determine BF, a better standardization of the definition and operationalization of BF, as well as of the period of time studied, is needed, as well as exhaustive studies examining the various factors that may determine BF.