Question

Another species of salamander, called a newt, exists along the coastal range of California. Newts have a terrestrial stage called an eft that has rough skin like the toads that you may be familiar with. When they are ready to breed they return to water where they sprout gills and breed. While on land the efts are quite vulnerable to predators, and have developed toxins for protection (toads secrete toxins too through their paratoid glands). Note that efts are bright orange.

4. Based on the information above and your knowledge of natural selection, explain why the Ensatina salamanders appear the way the do (both the coastal and more eastern populations). Be as specific as you can in applying the principles of natural selection.

5. Does knowing what the salamanders look like help you understand why Stebbins created separate subspecies for populations a (brown), b (red), and c (blue)? Explain using your knowledge of reproductive isolating mechanisms.

6. Assuming that the Ensatina complex expanded it range and radiated from only one of these populations of salamanders (traveling either north or south), which one would you predict was the original population and in which direction did they radiate? Explain your reasoning.

Answer 1

QUESTION NO:4

COLOR CHANGING MUTATIONS ARE SOMETIMES HELPFUL FOR INDIVIDUALS TO MATCH THEIR COLOR TO THAT OF THE ENVIRONMENT BETTER. NEWLY MUTATED INDIVIDUALS ARE MORE DIFFICULT FOR PREDATORS TO SPOT. THIS PROCESS IS CALLED NATURAL SELECTION FOR CRYPSIS.

ENSANTINA SALAMANDERS HAVE REGIONALLY SPECIFIC CRYPTIC COLORATION THAT WOULD AVOID PREDATORS. IN CALIFORNIA, THE PALATABLE YELLOW-EYED SALAMANDER CLOSELY RESEMBLES THE TOXIC CALIFORNIA NEWT AND THE ROUGH-SKINNED NEWT. IN SOME OTHER PARTS, IT IS CRYPTICALLY COLORED.

IT SHOWS HOW NATURAL SELECTION MIGHT AFFECT AN ORGANISM'S COLORATION. ENSANTINA SPECIES ARE DARKLY COLORED IN COASTAL CALIFORNIA TO MATCH THE DARK SUBSTRATE WHERE THEY OCCUR. A LEUCISTIC PALE PINK AND ORANGE MORPHS OF ENSANTINA ARE THERE IN MONTEREY COUNTRY. THEY ARE RARE IN NATURE WHEN COMPARED TO NORMALLY PIGMENTED ONES. THEY MIGHT BE EXPERIENCING SELECTION FOR CRYPSIS TO MATCH THEIR LIGHT, SANDY BACKGROUNDS

QUESTION NO:5

A COLLECTION OF EVOLUTIONARY MECHANISMS, BEHAVIOURS AND PHYSIOLOGICAL PROCESSES CRITICAL FOR SPECIATION IS KNOWN AS THE REPRODUCTIVE ISOLATION. MEMBERS OF DIFFERENT SPECIES ARE PREVENTED FROM PRODUCING OFFSPRING. BY REDUCING THE GENE FLOW BETWEEN RELATED SPECIES, THE INTEGRITY OF A SPECIES ARE MAINTAINED.

QUESTION NO:6

SCIENTISTS DECIPHERED THE EVOLUTION OF ENSANTINA BY THE PHENOMENON OF RING SPECIES.

IN THIS PROCESS, A SINGLE SPECIES BECOMES GEOGRAPHICALLY DISTRIBUTED IN A CIRCULAR PATTERN OVER A LARGE AREA. THE IMMEDIATE NEIGHBOURING POPULATION VARY SLIGHTLY BUT CAN INTERBREED. THE EVOLUTIONARY STORY AS DECIPHERED BY THE SCIENTISTS BEGINS IN THE NORTH. IT WAS PROBABLY THE ANCESTRAL POPULATION. THE POPULATION BECAME SPLIT AS IT EXPANDED SOUTH, IN CENRAL CALIFORNIA. TWO GROUPS THUS FORMED, ONE EVOLVED THEIR CRYPTIC COLORATION AND THE OTHER ALONG THE COAST GRADUALLY BACAME BRIGHTER.