[LTER-mcm-pi] 5 min gem for the week

[Diane McKnight]

Team, greetings from OSU. here's some  comments  that might relate to 
the discussion. I think that the stream diatoms are diverse because 
there are many "niches" to fill, ranging from the tolerance of 
dessication for years at time (such as the species that are dominant in 
Wormherder Creek), to vulnerability to removal by scour, and to nutrient 
requirements for N, P and Si. For nutrients accessible by the mats in 
the streams, there is actually variability at the patch scale due to 
hyporheic upwelling and downwelling  and with time due to flow regime 
influences on solute concentrations. Tyler's experiments with the 
nutrient diffusing substrates in the streams show significant nutrient 
effects.

This more dynamic and chemically variable habitat as a driver for 
diversity would be consistent with the 2 fold higher species richness 
for diatoms in stream matgs compared to diatoms in the more stable pond 
and lake mats.

Cheers Diane

On 9/16/2015 10:29 AM, Priscu, John wrote:
>
> Viruses or fungi would also be my guess.
>
> The lakes are stable on a large scale, but if they were stable at the 
> niche scale for microorganisms, then we should have competitive 
> exclusion—given the almost monospecific layering of phytoplankton in 
> the lakes, perhaps we do—but not sure how to explain the bacterial 
> diversity; maybe small scale differences in the flavor of DOC? The MCM 
> system definitely pushes the limits of typical ecological paradigms 
> that are used to assess diversity, stability and resilience.
>
> JP
>
> *From:*John Barrett [mailto:jebarre at vt.edu]
> *Sent:* Wednesday, September 16, 2015 10:22 AM
> *To:* Priscu, John
> *Cc:* mcm-pi at lists.lternet.edu
> *Subject:* Re: [LTER-mcm-pi] 5 min gem for the week
>
> Wow, that's uncanny John. I was just using the paradox of the plankton 
> in discussion with my grad students.
>
> My guess would be viruses to explain diversity in lakes. They are 
> otherwise too stable - unless we can invoke flood years as a physical 
> disruption that offsets competative exclusion. Are there data in the 
> cool years to show decreases in diversity? That would be a test of 
> whether floods acted to upset equilibrium in species composition.
>
> On Wed, Sep 16, 2015 at 12:15 PM, Priscu, John <jpriscu at montana.edu 
> <mailto:jpriscu at montana.edu>> wrote:
>
> Sorry that I missed the call yesterday—didn’t get home from Europe 
> until midnight and was not well organized—in other words, I forgot 
> about the call.
>
> Here would be my gem for the week: So, where does the MCM fit into 
> Terborgh’s scheme? We have few predators (I think we do—at least for 
> the lakes), yet biodiversity is relatively high. What replaces 
> predators in our system—Viruses? physical disruption? Maybe physical 
> disruption occurs faster than competitive exclusion, maintaining high 
> diversity? This kind of contemporaneous disequilibrium has been 
> proposed by Richerson et al. 1970 (attached) [Richerson was the chair 
> of my grad committee].
>
> JP
>
>
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>
>
>
> -- 
>
> J. E. Barrett, Ph.D.
> Associate Professor
> 2125 Derring Hall
> Department of Biological Sciences
> Virginia Tech
> Blacksburg VA, 24061
>
>
>
> N�n�r����)em�h�yhiם�w^��

-- 
Diane McKnight
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