vertical thermal gradients How do thermal tolerance limits differ - - PowerPoint PPT Presentation

 The effect of increasing environmental

temperature on the distribution of ectothermic species

 Connection to patterns of latitudinal and

vertical thermal gradients

 How do thermal tolerance limits differ among

species?

 What physiological systems set thermal tolerance

limits?

 Can temperature-adaptive protein evolution ‘keep

up with’ global warming?

 Do gene regulatory capacities of stenothermal and

eurythermal species differ?

 LT50 – acute lethal

temperature

 LT50 vs. latitude and height

• Results

ts: : tropi pical cal/s /subtr ubtrop

• pic

ical al species es and those e

• ccurr

urring ing highest st in the intertid tidal al zone had higher er LT50’s;  adaptiv ive e variation ation – more heat tolerant ant Congeneric Porcelain Crabs (genus Petrolisthes)

 MHT – maximal habitat

temperature

 MHT vs. LT50

• Re

Results ts: in latitudinal udinal groups ps the most heat-tole tolerant rant speci cies es are most t threatened tened by further her incr creases ases in temperature because current MHT’s reach or exceed LT50’s

• Intraspecific differences in thermal tolerance
• Whelks (Nucella canaliculata)

• Results:
• Inter-population differences in LT50
• Oregon – higher LT50’s
• Differences are most likely genetically based

• Conclusion: possibility of Oregon populations replacing

lower latitude pop’s that face local extinction from increasing temp’s

• Cardiac function = cause of

acute thermal death

• CTmax – critical thermal

maximum

• After this temperature, recovery

is not observed

• Congeneric Porcelain Crabs (genus Petrolisthes)

 LT50 vs. CTmax  LT50 = CTmax

• Conclusion: connection between whole

animal thermal tolerance and collapse of organ function

 Acclimation – change in physiological function occurring

as a result of alteration of an environmental parameter  usually experimental manipulation

 Acclimatization – change in physiological function

• ccurring as a result of complex natural environmental

changes

 Differences between warm-adapted and

temperate congeners of Petrolisthes

 Warm -

CTmax by 0.3 and 0.9 C

 Temperate -

CTmax by 1.2 and 2.2 C

 Conclusion – warm-adapted species are less

able to acclimate by increasing CTmax and LT50

• Congeneric species of Limpets (genus

Lottia)

• Higher whole-organism thermal tolerance

in southern species

• Orthologs of cytosolic malate

dehydrogenase (cMDH) for the two species are adapted to different temperatures

• Southern species – cMDH ortholog is more

thermally stable  it loses activity less rapidly than that of northern species

• Only a single amino acid difference

distinguishes the two orthologs

• Only a single amino acid substitution is necessary to

adaptively modify cMDH’s thermal sensitivity

• Sites of adaptive change influence cMDH’s conformational

mobility

• Numerous sites influencing energy changes linked to

conformational mobility

•  Adaptive change has a number of ‘targets’, and only
• ne needs to be ‘hit’ for adaptation
• Con
• nclu

lusio ion: Adaptive protein evolution might be able to ‘keep up with’ global warming

• Change from glycine  serine

• Genomic loss required for life at high temperatures
• Due to long evolutionary periods living at stable

conditions of low temperature

• Types:
• Protein coding genes  lost
• Mutations disrupting open reading frames of protein

coding genes

• Lesio

ions s in gene e regulat latory

• ry regions

ions

 Cold-adapted stenotherms

• Antarctic marine ectotherms

 Lesions in gene regulatory regions

• Negatively impacts acclimatization (vs. eurytherms)
• Eliminates ability to regulate gene expression (modify

transcriptional processes) in face of thermal stress

• Loss of HSR (heat-shock response)  unable to repair

damaged proteins caused by thermal stress

• Also, loss of protein-coding genes
• These impacts cause extreme stenothermality

 Warm-adapted, low latitude, high sites = most

threatened by further increases in temperature because:

• Proximity of LT50 and CTmax to MHT
• Limited ability to increase LT50 and CTmax through

acclimation

• ‘Losers’ are the warm-adapted eurytherms and

the extreme cold-adapted stenotherms