What is the minimum number of times that plants in the family Cupressaceae have crossed the Equator naturally? (note: human introductions don't count)
Nope! Extra points of course for saying which ones crossed and in which direction, and extra special points for roughly when ;-)
More, plant evolution and colonisation, and continental drift. But climate change and ice ages will have played their part too.
How far back can we go with continental drift? To Pangaea? 1. Austrocedrus, occasionally found just north of 0 degrees in the Ecuadorian Andes (extreme northern point of the range) 2. Cupressus, crossing from South to North on the African continent by continental drift (from Gondwanaland), and also on the Central American Peninsula by the same method and in the opposite direction (from Pangaea). 3. Juniperus, crossing from North to South on the Central American Peninsula (from Pangaea). 4. Papuacedrus, crossing South to North by continental drift at some point in the Cretaceous period. 5. Sequoia crossed from South to North at the extreme southern point of its range during the Permian (from Pagaea). 6. Sequoiadendron may also have crossed South to North at the same time. 7. Taxodium (specifically T. mucronatum) crossed South to North during the Permian. 8. Tetraclinis crossed South to North during the Permian to early Triassic. 9. Widdringtonia crossed South to North during the Triassic or possibly as late as the Cretaceous. So that gives us 9 crossings. You can get to 10 by means of evolution if you accept that Papuacedrus and Pilgerodendron are actually part of Libdocedrus. Closer? Or have I missed some?
michael didn't you ask "What is the minimum number of times that plants in the family Cupressaceae have crossed the Equator naturally? reading the question as originally posed. if it has crossed the equator then "Once" is the answer no? confused but then English is not my strong point!!
1. Austrocedrus, occasionally found just north of 0 degrees in the Ecuadorian Andes (extreme northern point of the range) If that's true, you've just extended its known northern limit by over 33° latitude! Sorry, no; it doesn't get north of 33°S. 2. Cupressus, crossing from South to North on the African continent by continental drift (from Gondwanaland), and also on the Central American Peninsula by the same method and in the opposite direction (from Pangaea). Nope, no Cupressus in the southern hemisphere. 3. Juniperus, crossing from North to South on the Central American Peninsula (from Pangaea). Nope, no Juniperus native in South America; in C America only reaches south to about 13°N. 4. Papuacedrus, crossing South to North by continental drift at some point in the Cretaceous period. YES! First correct answer (and perhaps the one I was least expecting!). It gets north to about 1°N on Halmahera, with the rest of its range between 2 and 11°S on New Guinea. But probably far more recent than the Cretaceous, more likely within the last one or two million years (the Australasian Plate on which Halmahera sits is moving north fairly fast as plate tectonics go). 5. Sequoia crossed from South to North at the extreme southern point of its range during the Permian (from Pagaea). 6. Sequoiadendron may also have crossed South to North at the same time. 7. Taxodium (specifically T. mucronatum) crossed South to North during the Permian. Nope, no verified fossil evidence for S Hemisphere Taxodium, Sequoia or Sequoiadendron ancestors. 8. Tetraclinis crossed South to North during the Permian to early Triassic. Nope, Tetraclinis is of northern origin, most closely allied to Platycladus (China), no evidence for its ever getting south of the Equator. 9. Widdringtonia crossed South to North during the Triassic or possibly as late as the Cretaceous. Nope, it has never been in the northern hemisphere; southern alliance related to Callitris etc. didn't you ask "What is the minimum number of times that plants in the family Cupressaceae have crossed the Equator naturally? reading the question as originally posed. if it has crossed the equator then "Once" is the answer no? The phylogeny of the family proves that there has been more than one equator-crossing event; the evidence shows there has been a minimum of X (I won't say how many, yet!) occasions. There could possibly be additional crossings, but they can't be proven from either the living species or the published fossil record (hope the English here isn't too complex!!).
YES! Equator crossing #2, south to about 18°S. Unlike Papuacedrus, junipers have picked up the trick of fast long-distance dispersal by birds. Not got all the answers yet though! There's more!
How about Callitropsis vietnamensis? From South of equator to North by way of Plate tectonics/continental drift?
Not sure what you will say about this one!!!!! Cupressus lusitanica. In India... South to North, plate tectonics. This article seems to be saying that C.lusitanica originated in India and that it is different from other C.lusitanicas in the northern hemisphere. http://64.233.183.132/search?q=cach...sus+lusitanica+india&hl=en&ct=clnk&cd=3&gl=uk
Notoriously unreliable author ;-) Cupressus lusitanica is from Mexico, but was very early introduced by man (15th century, one of the first plants brought over from the New World) and has long been naturalised in India after being taken there by the Portuguese.
YEP! That's Equator crossings #3 and #4, and completes the total. Not too relevant, as it happened well after event #4 (since Callitris, Widdringtonia, Fitzroya, etc., also diverged post-#4, but pre-these), and (except for the recent re-crossing by Papuacedrus) hasn't made further crossings
