130
ment at elevated temperatures. Nevertheless, this form
attained sexual maturity only one developmental stage
earlier than normal, and neotenic characteristics were
not evident. The upper lethal temperature seems to be
somewhat lower than for E. magdalenensis, but the
exact level could not be determined in nature.
Observations of mixed populations of both species
in the lower Magdalena Valley, their relative numbers,
and the topographic and climatic conditions of different
ponds, indicates that E. magdalenensis survives in the
extremely hot, frequently very shallow ponds, whereas
E. colombiensis thrives in the deeper and cooler ponds.
In extreme cases, only one species was present, but
normally the two forms appeared together. Statistical
analyses have not yet been conducted, but it is clear
that the relative numbers of each species depends in
part on the absolute size and depth of the ponds, the
topographic location; and the variable combination of
climatic factors such as rainfall intensity, cloudiness
and solar radiation - factors that ultimately determine
temperature, salinity, and especially the duration of the
freshwater habitat. Also to be considered are the past
climatic conditions of the ponds and the resulting egg
banks left by former generations.
In all cases, E. magdalenensis is adapted to survive
in more arid zones, and E. colombiensis is favored in
more moderate climates. Nevertheless, the two species
survive in mixed populations when the two meteorological conditions occur in an intermittent manner
without a clearly definite local climate on a longerterm scale.
As mentioned above, I have not yet studied the
ecological adaptations of Eulimnadia cf geayi, which
occurs in the lower Magdalena Valley within the same
areas as the two other forms. This part of the country
is probably the southern limit of distribution of this
species, which overlaps somewhat the range of the
two others. This was probably the species that Daday
(1927) reported from Venezuela, but I have not yet
found this species in the adjacent areas of the northeastern corner of Colombia on the banks of the Orinoco.
On the other hand, insufficient information is available
concerning the conchostracans of the northern parts of
Colombia and the Caribbean areas, especially the very
interesting arid Guajira peninsula, in order to connect
the two known localities of this species.
The fourth Colombian species of the family Limnadiidae belongs to the genus Limnadia. This form,
Limnadia orinoquiensis Roessler, 1991, is clearly
restricted to the forest regions in southeast Colombia, near the Orinoco. I found this species in acidic
ponds with characteristic black water in clearings of
the rain forest. The low pH of this water caused by
its content of humic acids, seems to be one of the
essential distribution factors. This species is obviously
the forest version of the open savannah conchostracan
fauna in the northwest and northeast of the Colombian Llanos (mainly Eulimnadia forms). Distribution
of L. orinoquiensis in the south and the southwest in the
very extensive tropical rain forests drained by the main
Colombian tributaries of the Orinoco and Amazon is
unknown (Fig. 1).
Lynceidae
The family Lynceidae is represented in Colombia by
the two genera Paralimnetis and Lynceus. This family
(with four Colombian species currently recognized),
is regionally distributed within the country. Ecological
differences among species are not easily recognizable,
but lynceids apparently prefer somewhat deeper ponds
of moderate temperature.
Paralimnetis mapimi Maeda-Martinez, 1987, is
restricted to the upper Magdalena Valley and occurs
sympatrically with E. magdalenensis. Nevertheless,
this coexistence is limited to certain ponds with a minimal duration of six to seven days. The life cycle of this
species is clearly not adapted to the very short lasting
waters inhabited by E. magdalenensis (Roessler, 1989
and unpublished data). P. mapimi has been reported
from Mexico (Maeda-Martinez, 1987), but I am not
aware of specific ecological information.
Paralimnetis rapax Gurney, 1929, was originally reported from Paraguay. The present report is the
first note on the rediscovery of this species. P. rapax
is the largest of the Colombian Lynceidae. I found
it in larger ponds in the company of Eulimnadia
colombiensis and abundant populations of the anostracan Dendrocephalus sp. Within this community,
P. rapax occupies an intermediate position in its temporal occurrence within the somewhat overlapping succession of euphyllopods. The first species to disappear
is E. colombiensis, followed closely by Paralimnetis.
The anostracans develop the slowest and are the last to
disappear.
Lynceus aequatorealis Daday, 1927, has been
found in Colombia only in the middle and lower Magdalena Valley. The form was originally described by
Daday (1927) from Venezuela and redescribed by Martin & Belk (1988) from the type locality. I found
abundant populations of this form in larger ponds with
loamy bottoms. This species probably occurs also in
ment at elevated temperatures. Nevertheless, this form
attained sexual maturity only one developmental stage
earlier than normal, and neotenic characteristics were
not evident. The upper lethal temperature seems to be
somewhat lower than for E. magdalenensis, but the
exact level could not be determined in nature.
Observations of mixed populations of both species
in the lower Magdalena Valley, their relative numbers,
and the topographic and climatic conditions of different
ponds, indicates that E. magdalenensis survives in the
extremely hot, frequently very shallow ponds, whereas
E. colombiensis thrives in the deeper and cooler ponds.
In extreme cases, only one species was present, but
normally the two forms appeared together. Statistical
analyses have not yet been conducted, but it is clear
that the relative numbers of each species depends in
part on the absolute size and depth of the ponds, the
topographic location; and the variable combination of
climatic factors such as rainfall intensity, cloudiness
and solar radiation - factors that ultimately determine
temperature, salinity, and especially the duration of the
freshwater habitat. Also to be considered are the past
climatic conditions of the ponds and the resulting egg
banks left by former generations.
In all cases, E. magdalenensis is adapted to survive
in more arid zones, and E. colombiensis is favored in
more moderate climates. Nevertheless, the two species
survive in mixed populations when the two meteorological conditions occur in an intermittent manner
without a clearly definite local climate on a longerterm scale.
As mentioned above, I have not yet studied the
ecological adaptations of Eulimnadia cf geayi, which
occurs in the lower Magdalena Valley within the same
areas as the two other forms. This part of the country
is probably the southern limit of distribution of this
species, which overlaps somewhat the range of the
two others. This was probably the species that Daday
(1927) reported from Venezuela, but I have not yet
found this species in the adjacent areas of the northeastern corner of Colombia on the banks of the Orinoco.
On the other hand, insufficient information is available
concerning the conchostracans of the northern parts of
Colombia and the Caribbean areas, especially the very
interesting arid Guajira peninsula, in order to connect
the two known localities of this species.
The fourth Colombian species of the family Limnadiidae belongs to the genus Limnadia. This form,
Limnadia orinoquiensis Roessler, 1991, is clearly
restricted to the forest regions in southeast Colombia, near the Orinoco. I found this species in acidic
ponds with characteristic black water in clearings of
the rain forest. The low pH of this water caused by
its content of humic acids, seems to be one of the
essential distribution factors. This species is obviously
the forest version of the open savannah conchostracan
fauna in the northwest and northeast of the Colombian Llanos (mainly Eulimnadia forms). Distribution
of L. orinoquiensis in the south and the southwest in the
very extensive tropical rain forests drained by the main
Colombian tributaries of the Orinoco and Amazon is
unknown (Fig. 1).
Lynceidae
The family Lynceidae is represented in Colombia by
the two genera Paralimnetis and Lynceus. This family
(with four Colombian species currently recognized),
is regionally distributed within the country. Ecological
differences among species are not easily recognizable,
but lynceids apparently prefer somewhat deeper ponds
of moderate temperature.
Paralimnetis mapimi Maeda-Martinez, 1987, is
restricted to the upper Magdalena Valley and occurs
sympatrically with E. magdalenensis. Nevertheless,
this coexistence is limited to certain ponds with a minimal duration of six to seven days. The life cycle of this
species is clearly not adapted to the very short lasting
waters inhabited by E. magdalenensis (Roessler, 1989
and unpublished data). P. mapimi has been reported
from Mexico (Maeda-Martinez, 1987), but I am not
aware of specific ecological information.
Paralimnetis rapax Gurney, 1929, was originally reported from Paraguay. The present report is the
first note on the rediscovery of this species. P. rapax
is the largest of the Colombian Lynceidae. I found
it in larger ponds in the company of Eulimnadia
colombiensis and abundant populations of the anostracan Dendrocephalus sp. Within this community,
P. rapax occupies an intermediate position in its temporal occurrence within the somewhat overlapping succession of euphyllopods. The first species to disappear
is E. colombiensis, followed closely by Paralimnetis.
The anostracans develop the slowest and are the last to
disappear.
Lynceus aequatorealis Daday, 1927, has been
found in Colombia only in the middle and lower Magdalena Valley. The form was originally described by
Daday (1927) from Venezuela and redescribed by Martin & Belk (1988) from the type locality. I found
abundant populations of this form in larger ponds with
loamy bottoms. This species probably occurs also in