80
P.A. Hulley
cladogram. The sole Antarctic Pattern species (E. antarctica) appeared as
one of the most highly evolved members of the tribe.
Discussion
MATRIX-I data indicate that station affinities could be correlated with the
water temperature at 200 m (Fig. 1). The use of isotherms at this depth
appears to be particularly suitable in the interpretation of lanternfish catch
data from large, nonclosing, mesopelagic samplers [14,16]. The absolute
value of the temperature should be viewed only as an index of the
integrated quality of the water column. Latitudinal banding of the station
groups from north to south is suggested by Fig. lA. With some exceptions
(Fig. 2A,B), the distribution pattern types (generalized distribution tracts)
correspond to those given in the literature [3,6,16,17].
Species of the genera Electrona, Krefftichthys, Metelectrona and
Protomyctophum (tribe Electronini) and Gymnoscopelus (tribe
Gymnoscopelini) are considered to be members of the cold-water complex
of species [18]. Except for Metelectrona, all occur only in one pattern
type, namely the Broadly Antarctic Pattern (Fig. 2C). This suggests that
Broadly Antarctic species (i.e. species attaining sexual maturity
throughout their distribution range between the STC and the Antarctic
continental shelf break, and thereby demonstrating adaptation to a wide
range of environmental conditions) may be most ancestral.
Because of the limited number of characters (Table I), the cladogram
(Fig. 3) should be regarded only as a preliminary result. Greater resolution
of the various sub groupings is required. However in support of the above
hypothesis, the following should be noted: (1) the ancestor species (K.
anderssoni) possesses a Broadly Antarctic Pattern; and (2) other species
possessing this pattern type are restricted to the base of the cladogram (i.e.
the most ancestral species). The pattern type does not occur again in the
phylogeny of the tribe.
Such interpretation differs only slightly (and mainly in nomenclature)
from that proposed by White [8]. On the basis of surface water-mass
cladograms, White [8: Figs. 3-6] envisages a subdivision of the ancestral
Austral region into South Temperate and South Polar regions, brought
about by the deepening of the Drake Passage and the establishment of the
Circumpolar Current (Early Miocene). The species cladogram (Fig. 3)
indicates a somewhat more complex evolution in the distribution of the
Electronini than White's [8: Fig. 6] proposal of a subsequent subdivision
of the South Polar region into distinct Antarctic and subAntarctic
biogeographic provinces (Early-to-Middle Miocene). Species of the
P.A. Hulley
cladogram. The sole Antarctic Pattern species (E. antarctica) appeared as
one of the most highly evolved members of the tribe.
Discussion
MATRIX-I data indicate that station affinities could be correlated with the
water temperature at 200 m (Fig. 1). The use of isotherms at this depth
appears to be particularly suitable in the interpretation of lanternfish catch
data from large, nonclosing, mesopelagic samplers [14,16]. The absolute
value of the temperature should be viewed only as an index of the
integrated quality of the water column. Latitudinal banding of the station
groups from north to south is suggested by Fig. lA. With some exceptions
(Fig. 2A,B), the distribution pattern types (generalized distribution tracts)
correspond to those given in the literature [3,6,16,17].
Species of the genera Electrona, Krefftichthys, Metelectrona and
Protomyctophum (tribe Electronini) and Gymnoscopelus (tribe
Gymnoscopelini) are considered to be members of the cold-water complex
of species [18]. Except for Metelectrona, all occur only in one pattern
type, namely the Broadly Antarctic Pattern (Fig. 2C). This suggests that
Broadly Antarctic species (i.e. species attaining sexual maturity
throughout their distribution range between the STC and the Antarctic
continental shelf break, and thereby demonstrating adaptation to a wide
range of environmental conditions) may be most ancestral.
Because of the limited number of characters (Table I), the cladogram
(Fig. 3) should be regarded only as a preliminary result. Greater resolution
of the various sub groupings is required. However in support of the above
hypothesis, the following should be noted: (1) the ancestor species (K.
anderssoni) possesses a Broadly Antarctic Pattern; and (2) other species
possessing this pattern type are restricted to the base of the cladogram (i.e.
the most ancestral species). The pattern type does not occur again in the
phylogeny of the tribe.
Such interpretation differs only slightly (and mainly in nomenclature)
from that proposed by White [8]. On the basis of surface water-mass
cladograms, White [8: Figs. 3-6] envisages a subdivision of the ancestral
Austral region into South Temperate and South Polar regions, brought
about by the deepening of the Drake Passage and the establishment of the
Circumpolar Current (Early Miocene). The species cladogram (Fig. 3)
indicates a somewhat more complex evolution in the distribution of the
Electronini than White's [8: Fig. 6] proposal of a subsequent subdivision
of the South Polar region into distinct Antarctic and subAntarctic
biogeographic provinces (Early-to-Middle Miocene). Species of the