8. Phytogeographic Relationships and Regional Richness Patterns
147
genia) and at the sectional level (e.g., Dasyphyllum) (Cabrera, 1959).
Such disjunctions appear to have been produced mostly by regional
segregation resulting from development of aridity east of the Andes and
in the area of the Atacama in the Oligocene-Miocene interval (Arroyo,
Squeo, Armesto, & Villagran, 1988; Galli-Olliver, 1967). The links to
tropical latitudes are nevertheless complex, and there is evident relationship with the southern Gondwanaland track in some cases at an earlier
stage (e.g., Myrteola, Drimys) . Subtropical and tropical members of these
genera frequently prefer cool, upland habitats, and thus could have
migrated into southern South America in the Eocene cooling, occupying
the higher elevations of the incipient Andes, and descending to their
present lower elevations in southern South America as of the Pliocene.
However that primitive members can occur in the Chilean phytogeographical area in some genera (Antidaphne, Kuijt, 1988; Dasyphyllum ,
Cabrera, 1959; and Fuchsia section Quelusia, Berry, 1989), might indicate
northward movement along mountainous corridors .
As of the upper Tertiary, with the Andean uplift and development of
the cold Humboldt current along the Pacific coast, the rainforest zone
became progressively isolated with development of arid climates to the
east and north . At this stage, it became open to intrusion by new floristic
elements diversifying in adjacent vegetation types. Typical here are species
of Chiliotrichum and Adesmia, which are better represented in drier
communities and only just get into rainforest. A boreal track is also
suggested by the occurrence of such genera as Ribes, Empetrum, Baccharis,
and Berberis, common to the northern hemisphere, including Europe,
Asia, and North American rainforest. Most of these genera, judging by
their current distributions, would have reached southern South America
along the Andean chain. The bipolar distribution of Empetrum, nevertheless, is consistent with long-distance dispersal (Moore , Harbourne, &
Williams, 1970).
Relating to the late Tertiary and previous periods , the Chilean phytogeographic region also exhibits a very high level of endemism (Arroyo
et al., 1993). Twenty-eight genera of the total of 82 woody genera in
rainforest (34%) and one family (Aextoxicaceae) are regional endemics
entirely restricted to the Chilean phytogeographic region, defined as
the entire temperate forest zone of Chile bordering into Argentina,
together with the mediterranean shrublands of central Chile (Table 8.1).
Pilgerodendron and Fitzroya are practically restricted to the rainforest
habitat, as defined here, and can be considered as true rainforest endemic
genera . Empirical evidence suggests many of the endemic genera are of
great antiquity and that both Gondwanaland and Neotropical origins have
been involved. Such genera tend to be taxonomically isolated (e.g.,
Aextoxicon, Lardizabala , Boquila , Fitzroya) and 79% are monotypic,
suggesting relictual status. The systematic affinities of the family Aextoxicaceae, a major rainforest tree , are highly uncertain. Endemism is
147
genia) and at the sectional level (e.g., Dasyphyllum) (Cabrera, 1959).
Such disjunctions appear to have been produced mostly by regional
segregation resulting from development of aridity east of the Andes and
in the area of the Atacama in the Oligocene-Miocene interval (Arroyo,
Squeo, Armesto, & Villagran, 1988; Galli-Olliver, 1967). The links to
tropical latitudes are nevertheless complex, and there is evident relationship with the southern Gondwanaland track in some cases at an earlier
stage (e.g., Myrteola, Drimys) . Subtropical and tropical members of these
genera frequently prefer cool, upland habitats, and thus could have
migrated into southern South America in the Eocene cooling, occupying
the higher elevations of the incipient Andes, and descending to their
present lower elevations in southern South America as of the Pliocene.
However that primitive members can occur in the Chilean phytogeographical area in some genera (Antidaphne, Kuijt, 1988; Dasyphyllum ,
Cabrera, 1959; and Fuchsia section Quelusia, Berry, 1989), might indicate
northward movement along mountainous corridors .
As of the upper Tertiary, with the Andean uplift and development of
the cold Humboldt current along the Pacific coast, the rainforest zone
became progressively isolated with development of arid climates to the
east and north . At this stage, it became open to intrusion by new floristic
elements diversifying in adjacent vegetation types. Typical here are species
of Chiliotrichum and Adesmia, which are better represented in drier
communities and only just get into rainforest. A boreal track is also
suggested by the occurrence of such genera as Ribes, Empetrum, Baccharis,
and Berberis, common to the northern hemisphere, including Europe,
Asia, and North American rainforest. Most of these genera, judging by
their current distributions, would have reached southern South America
along the Andean chain. The bipolar distribution of Empetrum, nevertheless, is consistent with long-distance dispersal (Moore , Harbourne, &
Williams, 1970).
Relating to the late Tertiary and previous periods , the Chilean phytogeographic region also exhibits a very high level of endemism (Arroyo
et al., 1993). Twenty-eight genera of the total of 82 woody genera in
rainforest (34%) and one family (Aextoxicaceae) are regional endemics
entirely restricted to the Chilean phytogeographic region, defined as
the entire temperate forest zone of Chile bordering into Argentina,
together with the mediterranean shrublands of central Chile (Table 8.1).
Pilgerodendron and Fitzroya are practically restricted to the rainforest
habitat, as defined here, and can be considered as true rainforest endemic
genera . Empirical evidence suggests many of the endemic genera are of
great antiquity and that both Gondwanaland and Neotropical origins have
been involved. Such genera tend to be taxonomically isolated (e.g.,
Aextoxicon, Lardizabala , Boquila , Fitzroya) and 79% are monotypic,
suggesting relictual status. The systematic affinities of the family Aextoxicaceae, a major rainforest tree , are highly uncertain. Endemism is