AboutZoos, Since 2008


Ancient insects shed light on biodiversity

pub­lished 13 Feb­ru­ary 2013 | mod­i­fied 13 Feb­ru­ary 2013
Fossil flySimon Fraser Uni­ver­sity evo­lu­tion­ary biol­o­gists Bruce Archibald and Rolf Math­ewes, and Bran­don Uni­ver­sity biol­o­gist David Green­wood, have dis­cov­ered that mod­ern trop­i­cal moun­tains’ diver­sity pat­terns extended up into Canada about 50 mil­lion years ago.

Their find­ings con­firm an influ­en­tial the­ory about change in mod­ern species diver­sity across moun­tains, and pro­vide evi­dence that global bio­di­ver­sity was greater in ancient times than now. The research was pub­lished on Feb­ru­ary 1 in the sci­en­tific jour­nal Palaeo­geog­ra­phy, Palaeo­cli­ma­tol­ogy, Palaeoe­col­ogy.

Some­times it helps to look to the ancient past to bet­ter under­stand how things work today
Bruce Archibald, evo­lu­tion­ary biol­o­gist, Simon Fraser Uni­ver­sity »

About 45 years ago, an evo­lu­tion­ary biol­o­gist at the Uni­ver­sity of Penn­syl­va­nia the­o­rised that change in species from site to site across moun­tain ranges in the trop­ics should be greater than in tem­per­ate lat­i­tudes.

Daniel Janzen rea­soned that the great dif­fer­ence between sum­mer and win­ter in tem­per­ate lat­i­tudes (high sea­son­al­ity) offers a wide win­dow to migrate across moun­tain­ous regions. The small dif­fer­ence in the trop­ics (low sea­son­al­ity) allows a very nar­row oppor­tu­nity, annu­ally. Con­se­quently, com­mu­ni­ties across trop­i­cal moun­tains should have fewer of the same species. Many stud­ies exam­in­ing mod­ern com­mu­ni­ties sup­port this the­ory.

Archibald, Math­ewes and Green­wood realised that fos­sil beds across a thou­sand kilo­me­tres of the ancient moun­tains of British Colum­bia and Wash­ing­ton pro­vided a unique lens through which to deepen eval­u­a­tion of this the­ory.

Fifty mil­lion years ago, when these fos­sil beds were laid down, the world had low sea­son­al­ity out­side of the trop­ics, right to the poles. Because of this, if Janzen’s the­ory is right, the pat­tern of bio­di­ver­sity that he described in mod­ern trop­i­cal moun­tains should have extended well into higher lat­i­tudes.

We found that insect species changed greatly across British Columbia’s and Wash­ing­ton State’s ancient moun­tain ranges, like in the mod­ern trop­ics,” Archibald says, “exactly as Janzen’s sea­son­al­ity hypoth­e­sis pre­dicted.

This implies that it’s the par­tic­u­lar sea­son­al­ity now found in the mod­ern trop­ics, not where that cli­mate is sit­u­ated glob­ally, that affects this bio­di­ver­sity pat­tern.” He adds: “Some­times it helps to look to the ancient past to bet­ter under­stand how things work today.”

The find­ings also bol­ster the idea that ancient Earth was a much more diverse world than now with many more species.

(Source: Simon Fraser Uni­ver­sity media release, 07.02.2013)
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