Time and space frame of Diestramima evolution
The results of biogeographic analysis of all genetic samples (Fig. 5)
are basically consistent with the conclusions drawn by Allegrucci &
Sbordoni (2019). With the gradual disintegration of Pangea,
Rhaphidophoroidea is divided into two clades. The ancestors of
Dolichopodainae and Troglophilinae are mainly distributed in Laurasia
and the ancestors of Aemodogryllinae and Rhaphidophorinae are mainly
distributed in Gondwana. With the Indian subcontinent drift and
collision with Eurasia, the separation of the two clades Aemodogryllinae
and Rhaphidophorinae were formed gradually.
In the Paleogene period, we found that the separation of genusDiestramima from Diestrammena diverged at 33.90Ma (95%
HDP: 18.85–54.36 Ma) and can also be regarded as the separation of
tribe Diestramimini and Aemodogryllini. During this epoch, one of the
most significant climate changes on Earth since the Cenozoic era
occurred: the Eocene/ Oligocene boundary cooling event. It is
characterized by the rapid change of the Earth’s climate from the
previous Greenhouse to Icehouse, and the emergence of Ice sheets in
Antarctica is accompanied by a significant drop in global temperature
(Sun et al ., 2014). A drop in global temperatures may eventually
lead to the divergence of Aemodogryllini, which is more resilient to
cold conditions and can be dispersed to a wider area. The extreme
temperature rise of the Paleocene-Eocene thermal maximum did not affect
the diverged of the Aemodogryllinae and Rhaphidophorinae ancestors, and
may have only intensified their dispersal in the Oriental realm.
In the Neogene period, the first major separation time of the genusDiestramima diverged at 8.32Ma (95% HDP: 4.84–12.88 Ma). At
this time, temperatures began to warm during the Miocene, and various
tectonic processes occurred due to the collision and compression of
continental plate drift and the intensification of mountain building.
Among them, the Himalayan orogeny had the most profound impact on China
(Li et al ., 2011). It transformed the planetary wind system in
mainland China from early Miocene to monsoon wind system; the arid
inland areas in northwest China and the monsoon areas in east China
began to form. Until the late Miocene, the climate pattern of humid
southeast and arid northwest was basically formed. Paleoclimate changes
peaked during the Miocene and gradually shaped the modern climate
patterns that prevail today (Zachos et al ., 2001). The humid
climate in the eastern area and the sea level caused by warming
temperatures may cause some species in Diestramima to gradually
migrate east and north, and eventually become isolated due to the
frequent mountain building activities. In Fig. 5, the differentiation inDiestramima has a certain lag in this gradually humid and warm
climate, a reasonable explanation is that their mating behavior is
dependent on broadleaf shrubs or dwarf trees. Due to the monsoon climate
change, the relationship between the plant communities and vegetation
types in Eastern China during this period is also undergoing changes
(Jacques et al ., 2011; Su et al ., 2013; Li et al .,
2015; Zhang et al ., 2015). We found that in the males of the
genus Diestramima , they will stay in place after the ejaculation
is over and continue to lift and press the female genitalia, and the
frequency and method of this behavior vary according to the species. We
believe that this behavior may speed up the sperm entry into the female
body while also preventing or slowing down the rate at which the female
eats the spermatophore. Correspondingly, all species inDiestramima we have observed will choose dwarf trees, shrubs and
ferns with large leaves as their venues for this mating behavior. This
behavior has not been found in other species in the family
Aemodogryllinae.
The genus Diestramima diverge into two clades in the late
Miocene. A clade species are all from the southeast border of China and
countries in Southeast Asia, including D . conica (similar
to the species of Myanmar), D . yunnanensis (similar to the
species of Laos), D . subtilis (similar to the species of
Vietnam) and D . major (distributed in Vietnam and China),
and another clade species are almost all from inland China. During this
period, the uplift of the Himalayan-Tibetan Plateau led to increased
mountain folds in southwestern China and further changes in the Asian
seasonal pattern (An et al ., 2001). The ancestors of the genusDiestramima have dispersal to Guizhou, Hunan and deeper inland
areas of China from the end of the Pliocene to the early Pleistocene.
Three most widely distributed species of the genus Diestramima(D . austrosinensis , D . beybienkoi , D .intermedia ) in inland areas of China diverged almost at the same
time (2.54–1.02 Ma). The temperature drop and ice sheet increase
brought about by the Quaternary glaciation also affected their spread at
this time. The distribution and ancestral proliferation characteristics
of the genus Diestramima in China are very similar to the
ancestral distribution characteristics of the genus Sinocyrtaspis(Wang et al ., 2020) and the four genera of Catantopidae (Xuet al ., 2003) in China. The mountainous region of southern Yunnan
is one of the important origins of these grasshopper genera of
Catantopidae ancestors. The centres of origin of Sinocyrtaspiswere Hunan and north-east Guangxi, and they spread with this place as
the center. This may be one of the dispersal paths of Orthoptera in
China.